- From: Roy T. Fielding <fielding@gbiv.com>
- Date: Thu, 20 Sep 2012 00:24:09 -0700
- To: "public-tracking@w3.org (public-tracking@w3.org)" <public-tracking@w3.org>
Below is a plain text version of the generated source of the current
editors' draft for tracking preference expression (DNT), which may be
useful to folks who find it easier to respond in email with context
than to make comments indirectly by section number.
....Roy
----------------------------------------------------------------------
W3C
Tracking Preference Expression (DNT)
W3C Editor's Draft 14 September 2012
This version:
http://www.w3.org/2011/tracking-protection/drafts/tracking-dnt.html
Latest published version:
http://www.w3.org/TR/tracking-dnt/
Latest editor's draft:
http://www.w3.org/2011/tracking-protection/drafts/tracking-dnt.html
Editors:
Roy T. Fielding, Adobe
David Singer, Apple
Copyright (c) 2011-2012 W3C(R) (MIT, ERCIM, Keio), All Rights Reserved.
W3C liability, trademark and document use rules apply.
----------------------------------------------------------------------
Abstract
This specification defines the technical mechanisms for expressing a
tracking preference via the DNT request header field in HTTP, via an HTML
DOM property readable by embedded scripts, and via properties accessible
to various user agent plug-in or extension APIs. It also defines
mechanisms for sites to signal whether and how they honor this preference,
both in the form of a machine-readable tracking status resource at a
well-known location and via a Tk response header field, and a mechanism
for allowing the user to approve site-specific exceptions to DNT as
desired.
Status of This Document
This section describes the status of this document at the time of its
publication. Other documents may supersede this document. A list of
current W3C publications and the latest revision of this technical report
can be found in the W3C technical reports index at http://www.w3.org/TR/.
This document is an editors' strawman reflecting a snapshot of live
discussions within the Tracking Protection Working Group. It does not yet
capture all of our work. For example, we have issues that are [PENDING
REVIEW] with complete text proposals that have not yet made it into this
draft. Text in blue boxes presents multiple options the group is
considering. An issue tracking system is available for recording raised,
open, pending review, closed, and postponed issues regarding this
document.
This document was published by the Tracking Protection Working Group as an
Editor's Draft. If you wish to make comments regarding this document,
please send them to public-tracking@w3.org (subscribe, archives). All
feedback is welcome.
Publication as an Editor's Draft does not imply endorsement by the W3C
Membership. This is a draft document and may be updated, replaced or
obsoleted by other documents at any time. It is inappropriate to cite this
document as other than work in progress.
This document was produced by a group operating under the 5 February 2004
W3C Patent Policy. W3C maintains a public list of any patent disclosures
made in connection with the deliverables of the group; that page also
includes instructions for disclosing a patent. An individual who has
actual knowledge of a patent which the individual believes contains
Essential Claim(s) must disclose the information in accordance with
section 6 of the W3C Patent Policy.
Table of Contents
* 1. Introduction
* 2. Notational Conventions
* 2.1 Requirements
* 2.2 Formal Syntax
* 2.3 Terminology
* 3. Determining User Preference
* 4. Expressing a Tracking Preference
* 4.1 Expression Format
* 4.2 DNT Header Field for HTTP Requests
* 4.3 JavaScript API to Detect Preference
* 4.4 Plug-In APIs
* 4.5 Tracking Preference Expressed in Other Protocols
* 5. Communicating a Tracking Status
* 5.1 Overview
* 5.2 Tracking Status Value
* 5.3 Tracking Status Qualifier Values
* 5.4 Tk Header Field for HTTP Responses
* 5.4.1 Definition
* 5.4.2 Referring to a Request-specific Tracking Status
Resource
* 5.4.3 Indicating an Interactive Status Change
* 5.5 Tracking Status Resource
* 5.5.1 Site-wide Tracking Status
* 5.5.2 Request-specific Tracking Status
* 5.5.3 Representation
* 5.5.4 Status Checks are Not Tracked
* 5.5.5 Caching
* 5.6 Status Code for Tracking Required
* 5.7 Using the Tracking Status
* 5.7.1 Discovering Deployment
* 5.7.2 Preflight Checks
* 6. User-Granted Exceptions
* 6.1 Overview
* 6.2 Motivating Principles and Use Cases
* 6.3 Exception model
* 6.3.1 Introduction
* 6.3.2 Exception use by browsers
* 6.4 JavaScript API for Site-specific Exceptions
* 6.4.1 API to request site-specific exceptions
* 6.4.2 API to Cancel a Site-specific Exception
* 6.5 JavaScript API for Web-wide Exceptions
* 6.5.1 API to Request a Web-wide Exception
* 6.5.2 API to cancel a web-wide exception
* 6.6 Querying a host's exception status
* 6.7 Transfer of an exception to another third party
* 6.8 User interface guidelines
* 6.9 Exceptions without a DNT header
* 6.10 Fingerprinting
* A. Acknowledgements
* B. References
* B.1 Normative references
* B.2 Informative references
1. Introduction
The World Wide Web (WWW, or Web) consists of millions of sites
interconnected through the use of hypertext. Hypertext provides a simple,
page-oriented view of a wide variety of information that can be traversed
by selecting links, manipulating controls, and supplying data via forms
and search dialogs. A Web page is usually composed of many different
information sources beyond the initial resource request, including
embedded references to stylesheets, inline images, javascript, and other
elements that might be automatically requested as part of the rendering or
behavioral processing defined for that page.
Each of the hypertext actions and each of the embedded resource references
might refer to any site on the Web, leading to a seamless interaction with
the user even though the pages might be composed of information requested
from many different and possibly independent Web sites. From the user's
perspective, they are simply visiting and interacting with a single brand
- the first-party Web property - and all of the technical details and
protocol mechanisms that are used to compose a page representing that
brand are hidden behind the scenes.
It has become common for Web site owners to collect data regarding the
usage of their sites for a variety of purposes, including what led the
user to visit their site (referrals), how effective the user experience is
within the site (web analytics), and the nature of who is using their site
(audience segmentation). In some cases, the data collected is used to
dynamically adapt the content (personalization) or the advertising
presented to the user (targeted advertising). Data collection can occur
both at the first-party site and via third-party providers through the
insertion of tracking elements on each page. A survey of these techniques
and their privacy implications can be found in [KnowPrivacy].
People have the right to know how data about them will be collected and
how it will be used. Empowered with that knowledge, individuals can decide
whether to allow their online activities to be tracked and data about them
to be collected. Many Internet companies use data gathered about people's
online activities to personalize content and target advertising based on
their perceived interests. While some people appreciate this
personalization of content and ads in certain contexts, others are
troubled by what they perceive as an invasion of their privacy. For them,
the benefit of personalization is not worth their concerns about allowing
entities with whom they have no direct relationship to amass detailed
profiles about their activities.
Therefore, users need a mechanism to express their own preference
regarding tracking that is both simple to configure and efficient when
implemented. In turn, Web sites that are unwilling or unable to offer
content without such targeted advertising or data collection need a
mechanism to indicate those requirements to the user and allow them (or
their user agent) to make an individual choice regarding exceptions.
This specification defines the HTTP request header field DNT for
expressing a tracking preference on the Web, a well-known location (URI)
for providing a machine-readable tracking status resource that describes a
service's DNT compliance, the HTTP response header field Tk for resources
to communicate their compliance or non-compliance with the user's
expressed preference, and JavaScript APIs for determining DNT status and
requesting a user-granted exception.
A companion document, [TRACKING-COMPLIANCE], more precisely defines the
terminology of tracking preferences, the scope of its applicability, and
the requirements on compliant first-party and third-party participants
when an indication of tracking preference is received.
Issue 136: Resolve dependencies of the TPE on the compliance specification
The WG has not come to consensus regarding the definition of tracking and
the scope of DNT. As such, a site cannot actually say with any confidence
whether or not it is tracking, let alone describe the finer details in a
tracking status resource. This issue will be resolved by progress on the
TCS document, though its resolution is a necessary prerequisite to
understanding and correctly implementing the protocol defined by this
document.
2. Notational Conventions
2.1 Requirements
The key words MUST, MUST NOT, REQUIRED, SHOULD, SHOULD NOT, RECOMMENDED,
MAY, and OPTIONAL in this specification are to be interpreted as described
in [RFC2119].
2.2 Formal Syntax
This specification uses Augmented Backus-Naur Form [ABNF] to define
network protocol syntax and WebIDL [WEBIDL] for defining scripting APIs.
2.3 Terminology
This specification uses the term user agent to refer to any of the various
client programs capable of initiating HTTP requests, including, but not
limited to, browsers, spiders (web-based robots), command-line tools,
native applications, and mobile apps [HTTP11].
The term permitted use is used to indicate a restricted set of conditions
under which tracking is allowed in spite of the user's DNT preference.
The term user-granted exception is used when the user has permitted
tracking by a given third party, usually in the form of a site-specific
exception.
A companion document, [TRACKING-COMPLIANCE], defines many of the terms
used here, notably 'party', 'first party', and 'third party'.
3. Determining User Preference
The goal of this protocol is to allow a user to express their personal
preference regarding tracking to each server and web application that they
communicate with via HTTP, thereby allowing each service to either adjust
their behavior to meet the user's expectations or reach a separate
agreement with the user to satisfy all parties.
Key to that notion of expression is that it MUST reflect the user's
preference, not the choice of some vendor, institution, or network-imposed
mechanism outside the user's control. The basic principle is that a
tracking preference expression is only transmitted when it reflects a
deliberate choice by the user. In the absence of user choice, there is no
tracking preference expressed.
A user agent MUST offer users a minimum of two alternative choices for a
Do Not Track preference: unset or DNT:1. A user agent MAY offer a third
alternative choice: DNT:0.
If the user's choice is DNT:1 or DNT:0, the tracking preference is
enabled; otherwise, the tracking preference is not enabled.
A user agent MUST have a default tracking preference of unset (not
enabled) unless a specific tracking preference is implied by the decision
to use that agent. For example, use of a general-purpose browser would not
imply a tracking preference when invoked normally as SuperFred, but might
imply a preference if invoked as SuperDoNotTrack or UltraPrivacyFred.
Likewise, a user agent extension or add-on MUST NOT alter the tracking
preference unless the act of installing and enabling that extension or
add-on is an explicit choice by the user for that tracking preference.
We do not specify how tracking preference choices are offered to the user
or how the preference is enabled: each implementation is responsible for
determining the user experience by which a tracking preference is enabled.
For example, a user might select a check-box in their user agent's
configuration, install an extension or add-on that is specifically
designed to add a tracking preference expression, or make a choice for
privacy that then implicitly includes a tracking preference (e.g., Privacy
settings: high). The user-agent might ask the user for their preference
during startup, perhaps on first use or after an update adds the tracking
protection feature. Likewise, a user might install or configure a proxy to
add the expression to their own outgoing requests.
Although some controlled network environments, such as public access
terminals or managed corporate intranets, might impose restrictions on the
use or configuration of installed user agents, such that a user might only
have access to user agents with a predetermined preference enabled, the
user is at least able to choose whether to make use of those user agents.
In contrast, if a user brings their own Web-enabled device to a library or
cafe with wireless Internet access, the expectation will be that their
chosen user agent and personal preferences regarding Web site behavior
will not be altered by the network environment, aside from blanket
limitations on what resources can or cannot be accessed through that
network. Implementations of HTTP that are not under control of the user
MUST NOT generate or modify a tracking preference.
4. Expressing a Tracking Preference
4.1 Expression Format
When a user has enabled a tracking preference, that preference needs to be
expressed to all mechanisms that might perform or initiate tracking by
third parties, including sites that the user agent communicates with via
HTTP, scripts that can extend behavior on pages, and plug-ins or
extensions that might be installed and activated for various media types.
When enabled, a tracking preference is expressed as either:
DNT meaning
1 This user prefers not to be tracked on the target
site.
0 This user prefers to allow tracking on the target
site.
A user agent MUST NOT send a tracking preference expression if a tracking
preference is not enabled. This means that no expression is sent for each
of the following cases:
* the user agent does not implement this protocol;
* the user has not yet made a choice for a specific preference; or,
* the user has chosen not to transmit a preference.
In the absence of regulatory, legal, or other requirements, servers MAY
interpret the lack of an expressed tracking preference as they find most
appropriate for the given user, particularly when considered in light of
the user's privacy expectations and cultural circumstances. Likewise,
servers might make use of other preference information outside the scope
of this protocol, such as site-specific user preferences or third-party
registration services, to inform or adjust their behavior when no explicit
preference is expressed via this protocol.
4.2 DNT Header Field for HTTP Requests
The DNT header field is hereby defined as the means for expressing a
user's tracking preference via HTTP [HTTP11].
DNT-field-name = "DNT" ; case-insensitive
DNT-field-value = ( "0" / "1" ) *DNT-extension ; case-sensitive
DNT-extension = %x21 / %x23-2B / %x2D-5B / %x5D-7E
; excludes CTL, SP, DQUOTE, comma, backslash
A user agent MUST send the DNT header field on all HTTP requests if (and
only if) a tracking preference is enabled. A user agent MUST NOT send the
DNT header field if a tracking preference is not enabled.
The DNT field-value sent by a user agent MUST begin with the numeric
character "1" (%x31) if a tracking preference is enabled, and the
preference is for no tracking, and there is not a site-specific exception
for the origin server targeted by this request.
The DNT field-value sent by a user agent MUST begin with the numeric
character "0" (%x30) if a tracking preference is enabled, and the
preference is to allow tracking in general or by specific exception for
the origin server targeted by this request.
Example 1
GET /something/here HTTP/1.1
Host: example.com
DNT: 1
An HTTP intermediary MUST NOT add, delete, or modify the DNT header field
in requests forwarded through that intermediary unless that intermediary
has been specifically installed or configured to do so by the user making
the requests. For example, an Internet Service Provider MUST NOT inject
DNT: 1 on behalf of all of their users who have not expressed a
preference.
The remainder of the DNT field-value after the initial character is
reserved for future extensions. User agents that do not implement such
extensions MUST NOT send DNT-extension characters in the DNT field-value.
Servers that do not implement such extensions SHOULD ignore anything
beyond the first character.
DNT extensions are to be interpreted as modifiers to the main preference
expressed by the first digit, such that the main preference will be obeyed
if the recipient does not understand the extension. Hence, a
DNT-field-value of "1xyz" can be thought of as do not track, but if you
understand the refinements defined by x, y, or z, then adjust my
preferences according to those refinements. DNT extensions can only be
transmitted when a tracking preference is enabled.
The extension syntax is restricted to visible ASCII characters that can be
parsed as a single word in HTTP and safely embedded in a JSON string
without further encoding (section 5.5.3 Representation). Since the DNT
header field is intended to be sent on every request, when enabled,
designers of future extensions ought to use as few extension characters as
possible.
Note
This document does not have any implied or specified behavior for the
user-agent treatment of cookies when DNT is enabled.
4.3 JavaScript API to Detect Preference
A doNotTrack attribute on the Navigator interface [NAVIGATOR] (e.g., the
window.navigator object) is hereby defined as the means for expressing the
user's general tracking preference to scripts running within a top-level
page. A user agent MUST provide a doNotTrack attribute on the Navigator
interface for each top-level page.
partial interface Navigator {
readonly attribute DOMString doNotTrack;
};
doNotTrack of type DOMString, readonly
When a tracking preference is enabled, the doNotTrack attribute
for each top-level page MUST have the same string value that would
be sent in a DNT-field-value (section 4.2 DNT Header Field for
HTTP Requests) to an origin server that does not have any
corresponding user-granted exceptions. When a tracking preference
is not enabled, the doNotTrack attribute for each top-level page
MUST have a value of null.
The doNotTrack attribute only provides the user's general tracking
preference, independent of any user-granted exceptions or out-of-band
consent. A script wishing to determine the specific tracking preference
for a given document origin is expected to use the API in section 6.6
Querying a host's exception status.
A user agent MUST provide a doNotTrack attribute value that is consistent
with the user's current tracking preference that would be expressed via
the DNT header field. However, changes to the user's preference might
occur between the time when the APIs are checked and an actual request is
made. A server MUST treat the user's most recently received preference as
authoritative.
Issue 84: Make DNT status available to JavaScript
[PENDING REVIEW] Updated text in this section.
Issue 116: How can we build a JS DOM property which doesn't allow inline
JS to receive mixed signals?
[PENDING REVIEW] Updated text in this section.
4.4 Plug-In APIs
User agents often include user-installable component parts, commonly known
as plug-ins or browser extensions, that are capable of making their own
network requests. From the user's perspective, these components are
considered part of the user agent and thus ought to respect the user's
configuration of a tracking preference. However, plug-ins do not normally
have read access to the browser configuration.
Note
It is unclear whether we need to standardize the plug-in APIs or if we
should rely on it being defined per user agent based on general advice
here. No plug-in APIs have been proposed yet.
4.5 Tracking Preference Expressed in Other Protocols
A user's tracking preference is intended to apply in general, regardless
of the protocols being used for Internet communication. The protocol
expressed here is specific to HTTP communication; however, the semantics
are not restricted to use in HTTP; the same semantics may be carried by
other protocols, either in future revisions of this specification, or in
other specifications.
When it is known that the user's preference is for no tracking, compliant
services are still required to honor that preference, even if other
protocols are used. For example, redirecting to another protocol in order
to avoid receipt of the header is not compliant.
Note
The last paragraph may be more appropriate in the compliance document, as
it discusses compliance.
5. Communicating a Tracking Status
5.1 Overview
The primary goals of this protocol-expressing the user's preference and
adhering to that preference-can be accomplished without any response from
the server. However, the protocol also seeks to improve the transparency
of tracking behavior by providing a machine-readable means for discovering
claims of compliance and determining the current tracking status.
Unfortunately, providing a dynamic indication of tracking compliance on
every HTTP response is not feasible, since it would have the effect of
disabling caching for the entire Web. Instead, this protocol defines a
combination of response mechanisms that allow the information to be
communicated without making every response dynamic.
This section explains how a user agent MAY discover an origin server's
tracking status for a given resource. It defines a REQUIRED site-wide
tracking status resource at a specific well-known location and an OPTIONAL
space of request-specific tracking status resources for sites where the
tracking status might vary based on data within the request. It also
defines a Tk response header field that MAY be sent in any HTTP response,
MUST be sent in responses to requests that modify the tracking status, and
MAY direct the user to a request-specific tracking status resource
applicable to the current request.
Issue 120: Should the response header be mandatory (MUST) or recommended
(SHOULD)
[PENDING REVIEW] The site-wide resource is mandatory; the header field is
optional, except for the single MUST case above.
Issue 124: Alternative DNT implementations that replace HTTP headers with
something else
[PENDING REVIEW] The tracking status resource minimizes bandwidth usage
because only a small proportion of user agents are expected to perform
active verification, status would only be requested once per site per day,
and the response can be extensively cached.
5.2 Tracking Status Value
A tracking status value is a short notation for communicating how a
designated resource conforms to the tracking protection protocol, as
defined by this document and [TRACKING-COMPLIANCE]. There is no form of
negative response; i.e., an origin server that does not wish to claim
conformance to this protocol would not supply a tracking status resource
and would not send a Tk header field in responses.
For a site-wide tracking status resource, the designated resource to which
the tracking status applies is any resource on the same origin server. For
a Tk response header field, the corresponding request target is the
designated resource and remains so for any subsequent request-specific
tracking status resource referred to by that field.
All of the tracking status mechanisms use a common format for the tracking
status value: a single character from a limited set. The meaning of each
allowed character is defined in the following table.
status meaning
N None: The designated resource does not perform
tracking of any kind, not even for a permitted use,
and does not make use of any data collected from
tracking.
1 First party: The designated resource is designed for
use within a first-party context and conforms to the
requirements on a first party. If the designated
resource is operated by an outsourced service
provider, the service provider claims that it
conforms to the requirements on a third party acting
as a first party.
3 Third party: The designated resource is designed for
use within a third-party context and conforms to the
requirements on a third party.
X Dynamic: The designated resource is designed for use
in both first and third-party contexts and
dynamically adjusts tracking status accordingly. If
X is present in the site-wide tracking status, more
information MUST be provided via the Tk response
header field when accessing a designated resource.
If X is present in the Tk header field, more
information will be provided in a request-specific
tracking status resource referred to by the
status-id. An origin server MUST NOT send X as the
tracking status value in the representation of a
request-specific tracking status resource.
C Consent: The designated resource believes it has
received prior consent for tracking this user, user
agent, or device, perhaps via some mechanism not
defined by this specification, and that prior
consent overrides the tracking preference expressed
by this protocol.
U Updated: The request resulted in a potential change
to the tracking status applicable to this user, user
agent, or device. A user agent that relies on a
cached tracking status SHOULD update the cache entry
with the current status by making a new request on
the applicable tracking status resource. An origin
server MUST NOT send U as a tracking status value
anywhere other than a Tk header field that is in
response to a state-changing request.
For the site-wide tracking status and Tk header field, the tracking status
values 1 and 3 indicate how the designated resource is designed to
conform, not the nature of the request. Hence, if a user agent is making a
request in what appears to be a third-party context and the tracking
status value indicates that the designated resource is designed only for
first-party conformance, then either the context has been misunderstood
(both are actually the same party) or the resource has been referenced
incorrectly. For the request-specific tracking status resource, an
indication of first or third party as the status value describes how the
resource conformed to that specific request, and thus indicates both the
nature of the request (as viewed by the origin server) and the applicable
set of requirements to which the origin server claims to conform.
The tracking status value is case sensitive, as defined formally by the
following ABNF.
tracking-v = "1" ; "1" - first-party
/ "3" ; "3" - third-party
/ %x43 ; "C" - consent
/ %x4E ; "N" - none
/ %x55 ; "U" - updated
/ %x58 ; "X" - dynamic
Issue 137: Does hybrid tracking status need to distinguish between first
party (1) and outsourcing service provider acting as a first party (s)
[PENDING REVIEW] No, in practice there may be dozens of service providers
on any given request. If the designated resource is operated by a service
provider acting as a first party, then the responsible first party is
identified by the policy link or the owner of the origin server domain.
This satisfies the use case of distinguishing between a service provider
acting for some other site and the same service provider acting on one of
its own sites.
5.3 Tracking Status Qualifier Values
When present, the tracking status qualifier member's value consists of a
string of characters indicating what permitted uses for tracking are being
used. Multiple qualifiers can be provided.
Issue
ISSUE-136: Resolve dependencies of the TPE on the compliance
specification.
The list of qualifiers is intended to match one to one to the permitted
uses identified by [TRACKING-COMPLIANCE], using references to the
definitions there. The list will then be updated accordingly.
qualifier meaning
Audit: Tracking is limited to that necessary for
a an external audit of the service context and the
data collected is minimized accordingly.
Ad frequency capping: Tracking is limited to
c frequency capping and the data collected is
minimized accordingly.
Fraud prevention: Tracking is limited to that
f necessary for preventing or investigating
fraudulent behavior and security violations; the
data collected is minimized accordingly.
Local constraints: Tracking is limited to what
l is required by local law, rule, or regulation
and the data collected is minimized accordingly.
Referrals: Tracking is limited to collecting
r referral information and the data collected is
minimized accordingly.
Qualifiers that indicate limitations on tracking correspond to the
specific permitted uses in [TRACKING-COMPLIANCE]. An origin server
indicating one or more of those permitted uses also indicates that it
conforms to the requirements associated with those permitted uses.
Multiple limitation qualifiers mean that multiple permitted uses of
tracking might be present and that each such use conforms to the
associated requirements. All limitation qualifiers imply some form of
tracking might be used and thus MUST NOT be provided with a tracking
status value of N (not tracking).
Future extensions to this protocol might define additional characters as
qualifiers from the ext-qualifier set (consisting of the remaining unused
lowercase letters, dot, dash, and underscore). Recipients SHOULD ignore
extension qualifiers that they do not understand.
The tracking qualifier value is case sensitive, as defined formally by the
following ABNF.
tracking-q = tracking-q-v*
tracking-q-v = %x61 ; "a" - audit
/ %x63 ; "c" - capping
/ %x66 ; "f" - fraud
/ %x6C ; "l" - local
/ %x72 ; "r" - referral
5.4 Tk Header Field for HTTP Responses
5.4.1 Definition
The Tk response header field is hereby defined as an OPTIONAL means for
indicating the tracking status that applied to the corresponding request
and as a REQUIRED means for indicating that a state-changing request has
resulted in an interactive change to the tracking status.
Tk-field-name = "Tk" ; case-insensitive
Tk-field-value = tracking-v [tracking-q] [ ";" status-id ]
The Tk field-value begins with a tracking status value (section 5.2
Tracking Status Value), optionally followed by one or more tracking
qualifiers (section 5.3 Tracking Status Qualifier Values), and then
optionally a semicolon and a status-id that refers to a request-specific
tracking status resource (section 5.4.2 Referring to a Request-specific
Tracking Status Resource).
For example, a Tk header field for a resource that claims not to be
tracking would look like:
Example 2
Tk: N
whereas a Tk header field for a resource that might perform tracking
(though not necessarily for every request) and conforms to the third-party
requirements of [TRACKING-COMPLIANCE], while claiming the audit exception,
would look like:
Example 3
Tk: 3a
Issue 107: Exact format of the response header?
[PENDING REVIEW] See the proposal in this section.
5.4.2 Referring to a Request-specific Tracking Status Resource
If an origin server has multiple, request-specific tracking policies, such
that the tracking status might differ depending on some aspect of the
request (e.g., method, target URI, header fields, data, etc.), the origin
server MAY provide an additional subtree of well-known resources
corresponding to each of those distinct tracking statuses. The OPTIONAL
status-id portion of the Tk field-value indicates which specific tracking
status resource applies to the current request.
status-id = 1*id-char ; case-sensitive
id-char = ALPHA / DIGIT / "_" / "-" / "+" / "=" / "/"
For example, a response containing
Example 4
Tk: 1;fRx42
indicates that the target resource claims to conform to the first-party
requirements of [TRACKING-COMPLIANCE] and that an applicable tracking
status representation can be obtained by performing a retrieval request on
/.well-known/dnt/fRx42
If a Tk field-value has a tracking status value of X (dynamic), then a
status-id MUST be included in the field-value.
5.4.3 Indicating an Interactive Status Change
We anticipate that interactive mechanisms might be used, beyond the scope
of this specification, that have the effect of asking for and obtaining
prior consent for tracking, or for modifying prior indications of consent.
For example, the tracking status resource's status-object defines a
control member that can refer to such a mechanism. Although such
out-of-band mechanisms are not defined by this specification, their
presence might influence the tracking status object's response value.
When an origin server provides a mechanism via HTTP for establishing or
modifying out-of-band tracking preferences, the origin server MUST
indicate within the mechanism's response when a state-changing request has
resulted in a change to the tracking status for that server. This
indication of an interactive status change is accomplished by sending a Tk
header field in the response with a tracking status value of U (updated).
Example 5
Tk: U
5.5 Tracking Status Resource
5.5.1 Site-wide Tracking Status
An origin server MUST provide a site-wide tracking status resource at the
well-known identifier [RFC5785]
/.well-known/dnt
(relative to the URI of that origin server) for obtaining information
about the potential tracking behavior of resources provided by that origin
server. A tracking status resource MAY be used for verification of DNT
support, as described in section 5.7 Using the Tracking Status.
A valid retrieval request (e.g., a GET in HTTP) on the well-known URI MUST
result in either a successful response containing a machine-readable
representation of the site-wide tracking status, as defined below, or a
sequence of redirects that leads to such a representation. A user agent
MAY consider failure to provide access to such a representation equivalent
to the origin server not implementing this protocol. The representation
MAY be cached, as described in section 5.5.5 Caching.
5.5.2 Request-specific Tracking Status
If an origin server has multiple, request-specific tracking policies, such
that the tracking status might differ depending on some aspect of the
request (e.g., method, target URI, header fields, data, etc.), the origin
server MAY provide an additional subtree of well-known resources
corresponding to each of those distinct tracking statuses. The Tk response
header field (section 5.4 Tk Header Field for HTTP Responses) can include
a status-id to indicate which specific tracking status resource applies to
the current request.
The tracking status resource space is defined by the following URI
Template [URI-TEMPLATE]:
/.well-known/dnt{/status-id}
where the value of status-id is a string of URI-safe characters provided
by a Tk field-value in response to a prior request. For example, a prior
response containing
Example 6
Tk: 1;ahoy
refers to the specific tracking status resource
/.well-known/dnt/ahoy
Resources within the request-specific tracking status resource space are
represented using the same format as a site-wide tracking status resource.
5.5.3 Representation
The representation of a tracking status resource shall be provided in the
"application/json" format [RFC4627] and MUST conform to the ABNF for
status-object (except that the members within each member-list MAY be
provided in any order).
The following example tracking status representation illustrates all of
the fields defined by this specification, most of which are optional.
Example 7
{
"tracking": "1",
"same-party": [
"example.com",
"example_vids.net",
"example_stats.com"
],
"third-party": [
"api.example.net"
],
"audit": [
"http://auditor.example.org/727073"
],
"policy": "/tracking.html",
"control": "http://example.com/your/data"
}
A tracking status representation consists of a single status-object
containing members that describe the tracking status applicable to the
designated resource.
status-object = begin-object member-list end-object
member-list = tracking ns tracking-v [tracking-q]
[ vs same-party ns same-party-v ]
[ vs third-party ns third-party-v ]
[ vs audit ns audit-v ]
[ vs policy ns policy-v ]
[ vs control ns control-v ]
*( vs extension )
A status-object MUST have a member named tracking that contains a single
character tracking status value (section 5.2 Tracking Status Value),
optionally followed by one or more tracking qualifiers (section 5.3
Tracking Status Qualifier Values) .
tracking = %x22 "tracking" %x22
For example, the following demonstrates a minimal tracking status
representation that is applicable to any resource that does not perform
tracking.
Example 8
{"tracking": "N"}
An OPTIONAL member named same-party MAY be provided with an array value
containing a list of domain names that the origin server claims are the
same party, to the extent they are referenced by the designated resource,
since all data collected via those references share the same data
controller.
same-party = %x22 "same-party" %x22
same-party-v = array-of-strings
An OPTIONAL member named third-party MAY be provided with an array value
containing a list of domain names for third-party services that might be
invoked while using the designated resource but do not share the same data
controller as the designated resource.
third-party = %x22 "third-party" %x22
third-party-v = array-of-strings
An OPTIONAL member named audit MAY be provided with an array value
containing a list of URI references to external audits of the designated
resource's tracking policy and tracking behavior in compliance with this
protocol. Preferably, the audit references are to resources that describe
the auditor and the results of that audit; however, if such a resource is
not available, a reference to the auditor is sufficient.
audit = %x22 "audit" %x22
audit-v = array-of-strings
An OPTIONAL member named policy MAY be provided with a string value
containing a URI-reference to a human-readable document that describes the
tracking policy for the designated resource. The content of such a policy
document is beyond the scope of this protocol and only supplemental to
what is described by this machine-readable tracking status representation.
policy = %x22 "policy" %x22
policy-v = string ; URI-reference
If the tracking status value is 1 and the designated resource is being
operated by an outsourced service provider on behalf of a first party, the
origin server MUST identify the responsible first party via the domain of
the policy URI, if present, or by the domain owner of the origin server.
If no policy URI is provided and the origin server domain is owned by the
service provider, then the service provider is the first party.
An OPTIONAL member named control MAY be provided with a string value
containing a URI-reference to a resource for giving the user control over
personal data collected by the designated resource (and possibly other
resources); a control member SHOULD be provided if the tracking status
value indicates prior consent (C). Such a control resource might include
the ability to review past data collected, delete some or all of the data,
provide additional data (if desired), or opt-in, opt-out, or otherwise
modify an out-of-band consent status regarding data collection. The design
of such a resource, the extent to which it can provide access to that
data, and how one might implement an out-of-band consent mechanism is
beyond the scope of this protocol.
control = %x22 "control" %x22
control-v = string ; URI-reference
Additional extension members MAY be provided in the status-object to
support future enhancements to this protocol. A user agent SHOULD ignore
extension members that it does not recognize.
extension = object
array-of-strings = begin-array
[ string *( vs string ) ]
end-array
ns = <name-separator (:), as defined in [[!RFC4627]]>
vs = <value-separator (,), as defined in [[!RFC4627]]>
begin-array = <begin-array ([), as defined in [[!RFC4627]]>
end-array = <end-array (]), as defined in [[!RFC4627]]>
begin-object = <begin-object ({), as defined in [[!RFC4627]]>
end-object = <end-object (}), as defined in [[!RFC4627]]>
object = <object, as defined in [[!RFC4627]]>
string = <string, as defined in [[!RFC4627]]>
true = <true, as defined in [[!RFC4627]]>
false = <false, as defined in [[!RFC4627]]>
null = <null, as defined in [[!RFC4627]]>
Note that the tracking status resource space applies equally to both
first-party and third-party services. An example of a third-party tracking
status is
Example 9
{
"tracking": "3",
"policy": "/privacy.html",
"control": "/your/data",
}
Issue 47: Should the response from the server indicate a policy that
describes the DNT practices of the server?
[PENDING REVIEW] The tracking status resource is a machine-readable policy
and provides a mechanism for supplying a link to a human-readable policy.
Issue 61: A site could publish a list of the other domains that are
associated with them
[PENDING REVIEW] The same-party and third-party members provide a means to
list first-party and third-party domains, respectively.
5.5.4 Status Checks are Not Tracked
When sending a request for the tracking status, a user agent SHOULD
include any cookie data [COOKIES] (set prior to the request) that would be
sent in a normal request to that origin server, since that data might be
needed by the server to determine the current tracking status. For
example, the cookie data might indicate a prior out-of-band decision by
the user to opt-out or consent to tracking by that origin server.
All requests on the tracking status resource space, including the
site-wide tracking status resource, MUST NOT be tracked, irrespective of
the presence, value, or absence of a DNT header field, cookies, or any
other information in the request. In addition, all responses to those
requests, including the responses to redirected tracking status requests,
MUST NOT have Set-Cookie or Set-Cookie2 header fields and MUST NOT have
content that initiates tracking beyond what was already present in the
request. A user agent SHOULD ignore, or treat as an error, any Set-Cookie
or Set-Cookie2 header field received in such a response.
5.5.5 Caching
If the tracking status is applicable to all users, regardless of the
received DNT-field-value or other data received via the request, then the
response SHOULD be marked as cacheable and assigned a time-to-live
(expiration or max-use) that is sufficient to enable shared caching but
not greater than the earliest point at which the service's tracking
behavior might increase. For example, if the tracking status response is
set to expire in seven days, then the earliest point in time that the
service's tracking behavior can be increased is seven days after the
policy has been updated to reflect the new behavior, since old copies
might persist in caches until the expiration is triggered. A service's
tracking behavior can be reduced at any time, with or without a
corresponding change to the tracking status resource.
If the tracking status is only applicable to all users that have the same
DNT-field-value, then the response MUST either be marked with a Vary
header field that includes "DNT" in its field-value or marked as not
reusable by a shared cache without revalidation with a Cache-Control
header field containing one of the following directives: "private",
"no-cache", "no-store", or "max-age=0".
If the tracking status is only applicable to the specific user that
requested it, then the response MUST include a Cache-Control header field
containing one of the following directives: "private", "no-cache", or
"no-store".
Regardless of the cache-control settings, it is expected that user agents
will check the tracking status of a service only once per session (at
most). A public Internet site that intends to change its tracking status
to increase tracking behavior MUST update the tracking status resource in
accordance with that planned behavior at least twenty-four hours prior to
activating that new behavior on the service.
A user agent that adjusts behavior based on active verification of
tracking status, relying on cached tracking status responses to do so,
SHOULD check responses to its state-changing requests (e.g., POST, PUT,
DELETE, etc.) for a Tk header field with the U tracking status value, as
described in section 5.4.3 Indicating an Interactive Status Change.
5.6 Status Code for Tracking Required
If an origin server receives a request with DNT:1, does not have
out-of-band consent for tracking this user, and wishes to deny access to
the requested resource until the user provides some form of user-granted
exception or consent for tracking, then the origin server SHOULD send an
HTTP error response with a status code of 409 (Conflict) and a message
body that describes why the request has been refused and how one might
supply the required consent or exception to avoid this conflict [HTTP11].
The 409 response SHOULD include a user authentication mechanism in the
header fields and/or message body if user login is one of the ways through
which access is granted.
Issue 128: HTTP error status code to signal that tracking is required?
[PENDING REVIEW] As defined by this section.
5.7 Using the Tracking Status
Note
This section is for collecting use cases that describe questions a user
agent might have about tracking status and how the protocol can be used to
answer such questions. More cases are needed.
5.7.1 Discovering Deployment
The presence of a site-wide tracking status representation is a claim that
the service conforms to this protocol for a given user agent. Hence,
deployment of this protocol for a given service can be discovered by
making a retrieval request on the site-wide tracking resource
/.well-known/dnt relative to the service URI.
If the response is an error, then the service does not implement this
standard. If the response is a redirect, then follow the redirect to
obtain the tracking status (up to some reasonable maximum of redirects to
avoid misconfigured infinite request loops). If the response is
successful, obtain the tracking status representation from the message
payload, if possible, or consider it an error.
5.7.2 Preflight Checks
A key advantage of providing the tracking status at a resource separate
from the site's normal services is that the status can be accessed and
reviewed prior to making use of those services and prior to making
requests on third-party resources referenced by those services.
A user agent MAY check the tracking status for a designated resource by
first making a retrieval request for the site-wide tracking status
representation, as described above, and then parsing the representation as
JSON to extract the Javascript status-object. If retrieval is unsuccessful
or parsing results in a syntax error, the user agent SHOULD consider the
site to be non-conformant with this protocol.
The status-object is supposed to have a member named tracking containing
the tracking status value. The meaning of each tracking status value is
defined in section 5.2 Tracking Status Value.
If the tracking status value is N, then the origin server claims that no
tracking is performed for the designated resource for at least the next 24
hours or until the Cache-Control information indicates that this response
expires.
If the tracking status value is not N, then the origin server claims that
it might track the user agent for requests on the URI being checked for at
least the next 24 hours or until the Cache-Control information indicates
that this response expires.
6. User-Granted Exceptions
6.1 Overview
This section is non-normative.
User-granted exceptions to Do Not Track, including site-specific
exceptions, are managed by the user agent. A resource should rely on the
DNT header it receives to determine the user's preference for tracking
with respect to that particular request. An API is provided so that sites
may request and check the status of exceptions for tracking.
We anticipate that many user-agents might provide a prompt to users when
this API is used, or to store exceptions. Questions of user interface
specifics - for granting, configuring, storing, syncing and revoking
exceptions - are explicitly left open to implementers.
Issue 144: What constraints on user agents should be imposed for
user/granted exceptions
[OPEN] but mostly addressed in the proposal here.
6.2 Motivating Principles and Use Cases
This section is non-normative.
The following principles guide the design of user-agent-managed
exceptions.
* Content providers may wish to prompt visitors to their properties to
opt back in to tracking for behavioral advertising or similar purposes
when they arrive with the Do Not Track setting enabled.
* Privacy-conscious users may wish to view or edit all the exceptions
they've granted in a single, consistent user interface, rather than
managing preferences in a different way on every content provider or
tracker's privacy page.
* Granting an exception in one context (while browsing a news site)
should not apply that exception to other contexts (browsing a medical
site) that may not be expected.
* Tracking providers should not ever have to second-guess a user's
expressed Do Not Track preference.
* The solution should not require cross-domain communication between a
first-party publisher and its third parties.
When asking for a site-specific exception, the top-level domain making the
request may be making some implicit or explicit claims as to the actions
and behavior of its third parties; for this reason, it might want to
establish exceptions for only those for which it is sure that those claims
are true. (Consider a site that has some trusted advertisers and analytics
providers, and some mashed-up content from less-trusted sites). For this
reason, there is support both for explicitly named sites, as well as
support for granting an exception to all third-parties on a given site
(site-wide exception, using the conceptual wild-card "*").
There are some cases in which a user may desire a site to be allowed to
track them on any top-level domain. An API is provided so that the site
and the user may establish such a web-wide exception.
6.3 Exception model
6.3.1 Introduction
This section describes the effect of the APIs in terms of a logical
processing model; this model describes the behavior, but should not be
read as mandating any specific implementation.
This API considers exceptions which are double-keyed to two domains: the
site, and the target. A user might - for instance - want AnalytiCo to be
allowed to track them on Example News, but not on Example Medical. To
simplify language used in this API specification, we define three terms:
* Top-Level Domain (TLD) is the domain name of the top-level document
origin of this DOM: essentially the fully qualified domain name in the
address bar.
* A target site is a domain name which is the target of an HTTP request,
and which may be an origin for embedded resources on the indicated
top-level domain.
* The document origin of a script is the domain of origin of the
document that caused that script to be loaded (not necessarily the
same as the origin of the script itself).
For instance, if the document at
http://web.exnews.com/news/story/2098373.html references the resources
http://exnews.analytico.net/1x1.gif and
http://widgets.exsocial.org/good-job-button.js, the top-level domain is
web.exnews.com; exnews.analytico.net and widgets.exsocial.org are both
targets.
Issue 112: How are sub-domains handled for site-specific exceptions?
[PENDING REVIEW] Should a request for a tracking exception apply to all
subdomains of the first party making the request? Or should a first party
explicitly list the subdomains that it's asking for? Similarly, should
third-party subdomains be allowed (e.g. *.tracker.com)?
Proposal: Exceptions are requested for fully-qualified domain names.
The domains that enter into the behavior of the APIs include:
* As described above, the document origin active at the time of the
call, and;
* Domain names passed to the API.
Domains that enter into the decision over what DNT header to be sent in a
given HTTP request include:
* The top-level domain of the current context;
* The target of the HTTP request.
Note
Note that these strict, machine-discoverable, concepts may not match the
definitions of first and third party; in particular, sites themselves need
to determine (and signal) when they get 'promoted' to first party by
virtue of user interaction; the UA will not change the DNT header it sends
them.
The calls cause the following steps to occur:
* First, the UA somehow confirms with the user that they agree to the
grant of exception, if not already granted;
* If they agree, then the UA adds to its local database one or more
site-pair duplets [document-origin, target]; one or other of these may
be a wild-card ("*");
* While the user is browsing a given site (top-level domain), and a DNT
header is to be sent to a target domain, if the duplet [top-level
domain, target domain] matches any duplet in the database, then a
DNT:0 header is sent, otherwise DNT:1 is sent.
Note
Note that a site may record no that it has previously asked for, and been
denied, an exception, if it wishes to avoid repeatedly asking the user for
an exception.
6.3.2 Exception use by browsers
If a user agrees to allow tracking by a target on the top-level domain,
this should result in two user-agent behaviors:
1. If requests to the target for resources that are part of the DOM for
pages on top-level domain include a DNT header, that header MUST be
DNT:0.
2. Responses to the JavaScript API indicated should be consistent with
this user preference (see below).
Issue 158: What is the effect of re-directs for content on the operation
of exceptions?
What is the effect of re-directs, when the source of the re-direct would
get a different DNT header than the target, using these matching rules?
Proposal: The re-direct is not relevant; each site gets the DNT header
controlled by the list of grants.
Issue 159: How do we allow sites that mash-in add-supported content to
maintain their own trusted third parties?
This model does not support mashed-up content which is in turn supported
by ads; it's not clear how to distinguish between embedded content which
is embedding ads (and hence the top-level domain stays the same) and
embedded content that should start a new context.
Proposal: For this version of the specification, we don't address this
corner case.
User-agents MUST handle each API request as a 'unit', granting and
maintaining it in its entirety, or not at all. That means that a
user-agent MUST NOT indicate to a site that a request for targets {a, b,
c} has been granted, and later remove only one or two of {a, b, c} from
its logical database of remembered grants. This assures sites that the set
of sites they need for operational integrity is treated as a unit. Each
separate call to an API is a separate unit.
When a user-agent receives an API request for an exception that already
exists (i.e. the grant is recorded in its database), it SHOULD bypass
asking the user to confirm, and simply re-confirm the grant to the caller.
Note
It is left up to individual user-agent implementations how to determine
and how and whether to store users' tracking preferences.
When an explicit list of domains is provided through the API, their names
might mean little to the user. The user might, for example, be told that
such-and-such top-level domain is asking for an exception for a specific
set of sites, rather than listing them by name; or the user-agent may
decide to ask the user for a site-wide exception, effectively ignoring the
list of domain names, if supplied.
Conversely, if a wild-card is used, the user may be told that the
top-level domain is asking for an exception for all third-parties that
are, or will be, embedded in it.
Issue 111: Different DNT values to signify existence of user-granted
exception
[POSTPONED] Should the user agent send a different DNT value to a first
party site if there exist user-granted exceptions for that first party?
(e.g. DNT:2 implies "I have Do Not Track enabled but grant permissions to
some third parties while browsing this domain")
Proposal: A previous proposal was that it can add itself to the list (i.e.
an exception for [site, site]) and then it will get DNT:0, but DNT:0 to a
first party means something different (that it can pass data to third
parties, and tracking is permitted). It would be better to have an
indication in the DNT header that one or more site-specific exceptions
exist for the given target (i.e. that there is at least one duplet in the
database with target as its first host name), for example "DNT:1E" where E
means you are a first party with one or more active exceptions.
6.4 JavaScript API for Site-specific Exceptions
6.4.1 API to request site-specific exceptions
[NoInterfaceObject]
interface NavigatorDoNotTrack {
void requestSiteSpecificTrackingException (TrackingResponseCallback callback, optional sequence<DOMString> arrayOfDomainStrings, optional optional siteName, optional optional explanationString, optional optional detailURI);
};
requestSiteSpecificTrackingException
Called by a page to request or confirm a user-granted tracking
exception.
Parameter Type Nullable Optional Description
callback TrackingResponseCallback * *
arrayOfDomainStrings sequence<DOMString> * *
siteName optional * *
explanationString optional * *
detailURI optional * *
Return type: void
[Callback, NoInterfaceObject]
interface TrackingResponseCallback {
void handleEvent (integer granted);
};
handleEvent
The callback is called by the user agent to indicate the user's
response.
Parameter Type Nullable Optional Description
granted integer * *
Return type: void
The requestSiteSpecificTrackingException method takes one mandatory
argument:
* callback, a method that will be called when the request is complete.
It also takes four optional arguments:
* arrayOfDomainStrings, a JavaScript array of strings,
* siteName, a user-readable string for the name of the top-level domain,
* explanationString, a short explanation of the request, and
* detailURI, a location at which further information about this request
can be found.
If the request does not include the arrayOfDomainStrings, then this
request is for a site-wide exception. Otherwise each string in
arrayOfDomainStrings specifies a target. When called,
requestSiteSpecificTrackingException MUST return immediately, then
asynchronously determine whether the user grants the requested
exception(s).
If the list arrayOfDomainStrings is supplied, the user-agent MAY choose to
ask the user to grant a site-wide exception. If it does so, and the user
agrees, it MUST indicate this in the response callback.
The execution of this API and the use of the resulting permission (if
granted) use the 'implicit' parameter, when the API is called, the
document origin. This forms the first part of the duplet in the logical
model, and hence in operation will be compared with the top-level domain.
The granted parameter passed to the callback is the user's response; The
response
* 0 indicates that user does not grant the exception on top-level domain
for the indicated targets.
* 1 indicates that the request was for specific targets and the the user
grants an exception on top-level domain for those specific targets.
* 2 indicates the user grants a site-wide exception on top-level domain
for all targets; the request may have been for specific targets or for
a site-wide exception.
If permission is granted for an explicit list, then the set of duplets
(one per target):
[document-origin, target]
is added to the database of remembered grants.
If permission is granted for a site-wide exception, then the duplets:
[document-origin, * ]
is added to the database of remembered grants.
A particular response to the API - like a DNT response header - is only
valid immediately, and users' preferences may change.
A user agent MAY use an interactive method to ask the user about their
preferences, so sites SHOULD NOT assume that the callback function will be
called immediately.
6.4.2 API to Cancel a Site-specific Exception
[NoInterfaceObject]
interface NavigatorDoNotTrack {
boolean removeSiteSpecificTrackingException ();
};
removeSiteSpecificTrackingException
Ensures that the database of remembered grants no longer contains
any duplets for which the first part is the current document
origin; i.e., no duplets [document-origin, target] for any target.
There is no callback. After the call has been made, it is assured
that there are no site-specific or site-wide exceptions for the
given top-level-domain.
No parameters.
Return type: boolean
This returns a boolean indicating, when true, that the call has succeeded,
and that the database of grants no longer contains, or very soon will no
longer contain, the indicated grant(s); when false, some kind of
processing error occurred.
6.5 JavaScript API for Web-wide Exceptions
6.5.1 API to Request a Web-wide Exception
[NoInterfaceObject]
interface NavigatorDoNotTrack {
void requestWebWideTrackingException (TrackingResponseCallback callback, optional siteName, optional optional explanationString, optional optional detailURI);
};
requestWebWideTrackingException
If permission is granted, then the single duplet [ * ,
document-origin] is added to the database of remembered grants.
The parameters are as described above in the request for
site-specific exceptions.
Parameter Type Nullable Optional Description
callback TrackingResponseCallback * *
siteName * *
explanationString optional * *
detailURI optional * *
Return type: void
Users may wish to configure exceptions for a certain trusted tracker
across all sites. This API requests the addition of a web-wide grant for a
specific site, to the database.
6.5.2 API to cancel a web-wide exception
[NoInterfaceObject]
interface NavigatorDoNotTrack {
boolean removeWebWideTrackingException ();
};
removeWebWideTrackingException
Ensures that the database of remembered grants no longer contains
the duplet [ * , document-origin]. There is no callback. After the
call has been made, the indicated pair is assured not to be in the
database. The same matching as is used for determining which
header to send is used to detect which entry (if any) to remove
from the database.
No parameters.
Return type: boolean
This returns a boolean indicating, when true, that the call has succeeded,
and that the database of grants no longer contains, or very soon will no
longer contain, the indicated grant; when false, some kind of processing
error occurred.
6.6 Querying a host's exception status
Issue 160: Do we need an exception-query API?
It might be useful, and 'complete the model', if we had a JS API that told
a host what its current exception status is in a given context.
Proposal: Specifically, an API QueryExceptionStatus() which examines the
document origin of the script, the current top-level domain and returns an
empty string if no DNT header would be sent to that document origin, or
the exact DNT header (DNT:1 or DNT:0) that would be sent otherwise.
[NoInterfaceObject]
interface NavigatorDoNotTrack {
DOMString requestDNTStatus ();
};
requestDNTStatus
Returns the same string value that would be sent in a
DNT-field-value (section 4.2 DNT Header Field for HTTP Requests)
to a target that is the document-origin of the request, in the
context of the current top-level domain. If no DNT header would be
sent (e.g. because a tracking preference is not enabled) the
return value is null.
No parameters.
Return type: DOMString
6.7 Transfer of an exception to another third party
A site may request an exception for one or more third party services used
in conjunction with its own offer. Those third party services may wish to
use other third parties to complete the request in a chain of
interactions. The first party will not necessarily know in advance whether
a known third party will use some other third parties.
If a user-agent sends a tracking exception to a given combination of
origin server and a named third party, the user agent will send DNT:0 to
that named third party. By receiving the DNT:0 header, the named third
party acquires the permission to track the user agent and collect the data
and process it in any way allowed by the legal system it is operating in.
Furthermore, the named third party receiving the DNT:0 header acquires at
least the right to collect data and process it for the given interaction
and any secondary use unless it receives a DNT:1 header from that
particular identified user agent.
The named third party is also allowed to transmit the collected data for
uses related to this interaction to its own sub-services and
sub-sub-services (transitive permission). The tracking permission request
triggered by the origin server is thus granted to the named third party
and its sub-services. This is even true for sub-services that would
normally receive a DNT:1 web-wide preference from the user-agent if the
user agent interacted with this service directly.
For advertisement networks this typically would mean that the collection
and auction system chain can use the data for that interaction and combine
it with existing profiles and data. The sub-services to the named third
party do not acquire an independent right to process the data for
independent secondary uses unless they, themselves, receive a DNT:0 header
from the user agent (as a result of their own request or the request of a
first-party). In our example of advertisement networks that means the
sub-services can use existing profiles in combination with the data
received, but they can not store the received information into a profile
until they have received a DNT:0 of their own.
A named third party acquiring an exception with this mechanism MUST make
sure that sub-services it uses acknowledge this constraint by requiring
the use of the appropriate tracking status value and qualifier, which is
"XX" (such as "tl"), from its sub-sub-services.
The permission acquired by the DNT mechanism does not override retention
limitations found in the legal system the content provider or the named
third party are operating in.
Issue
When the status values and qualifiers are fixed, the penultimate paragraph
will probably need adjusting to match. The use of "tl" (which meant
"tracking but only in accordance with local laws" when this text was
written) doesn't seem right, as the text talks, essentially, of the
sub-sub-service acting on behalf of the site that received the DNT:0
header, which might suggest something more like "CS" (service provision to
a third-party that received consent).
6.8 User interface guidelines
This section is non-normative.
User agents are free to implement exception management user interfaces as
they see fit. Some agents might provide a prompt to the user at the time
of the request. Some agents might allow users to configure this preference
in advance. In either case, the user agent responds with the user's
preference.
In general, it is expected that the site will explain, in its online
content, the need for an exception, and the consequences of granting or
denying an exception, to the user, and guide. The call to the API and the
resulting request for user confirmation should not be a 'surprise' to the
user, or require much explanation on the part of the user-agent.
A user agent that chooses to implement a prompt to present tracking
exception requests to the user might provide an interface like the
following:
Example 10
Example News (web.exnews.com) would like to confirm
that you permit tracking by a specific set of sites (click
here for their names).
Example News says:
These sites allow Example News to see how we're
doing, and provide useful features of the Example News
experience. [More info]
[Allow Tracking] [Deny Tracking Request]
In this example, the domains listed are those specified in
arrayOfDomainStrings, the phrase Example News is from siteName, and the
explanationString is displayed for the user with a More info link pointing
to detailURI.
The user agent might then store that decision, and answer future requests
based on this stored preference. A user agent might provide the user with
an interface to explicitly remove (or add) user-granted exceptions.
Users might not configure their agents to have simple values for DNT, but
use different browsing modes or other contextual information to decide on
a DNT value. What algorithm a user agent employs to determine DNT values
(or the lack thereof) is out of the scope of this specification.
In some user-agent implementations, decisions to grant exceptions may have
been made in the past (and since forgotten) or may have been made by other
users of the device. Thus, exceptions may not always represent the current
preferences of the user. Some user agents might choose to provide ambient
notice that user-opted tracking is ongoing, or easy access to view and
control these preferences. Users may desire options to edit exceptions
either at the time of tracking or in a separate user interface. This might
allow the user to edit their preferences for a site they do not trust
without visiting that site.
Issue 140: Do we need site-specific exceptions, i.e., concrete list of
permitted third parties for a site?
[PENDING REVIEW]: In this section; yes, as some sites may have a mix of
trusted/needed third parties, and others that either don't need to track,
or aren't as trusted, or both. But all sites are (a) told what they got
granted (list, or *) and (b) are assured that requests will be treated
'atomically'.
6.9 Exceptions without a DNT header
Sites might wish to request exceptions even when a user arrives without a
DNT header. Users might wish to grant affirmative permission to tracking
on or by certain sites even without expressing general tracking
preferences.
User agents MAY instantiate
NavigatorDoNotTrack.requestSiteSpecificTrackingException even when
navigator.doNotTrack is null. Sites SHOULD test for the existence of
requestSiteSpecificTrackingException before calling the method. If an
exception is granted in this context and the user-agent stores that
preference, a user agent may send a DNT:0 header even if a tracking
preference isn't expressed for other requests. Persisted preferences MAY
also affect which header is transmitted if a user later chooses to express
a tracking preference.
Note
Users might not configure their agents to have simple values for DNT, but
use different browsing modes or other contextual information to decide on
a DNT value. What algorithm a user agent employs to determine DNT values
(or the lack thereof) is out of the scope of this specification.
6.10 Fingerprinting
By storing a client-side configurable state and providing functionality to
learn about it later, this API might facilitate user fingerprinting and
tracking. User agent developers ought to consider the possibility of
fingerprinting during implementation and might consider rate-limiting
requests or using other heuristics to mitigate fingerprinting risk. User
agents SHOULD clear stored user-granted exceptions when the user chooses
to clear cookies or other client-side state.
A. Acknowledgements
This specification consists of input from many discussions within and
around the W3C Tracking Protection Working Group, along with written
contributions from Nick Doty (W3C/MIT), Rob van Eijk (Invited Expert),
Roy T. Fielding (Adobe), Tom Lowenthal (Mozilla), Jonathan Mayer
(Stanford), Aleecia M. McDonald (Mozilla), Matthias Schunter (IBM),
John Simpson (Consumer Watchdog), David Singer (Apple), Rigo Wenning
(W3C/ERCIM), Shane Wiley (Yahoo!), and Andy Zeigler (Microsoft).
The DNT header field is based on the original Do Not Track submission by
Jonathan Mayer (Stanford), Arvind Narayanan (Stanford), and Sid Stamm
(Mozilla). The DOM API for NavigatorDoNotTrack is based on the Web
Tracking Protection submission by Andy Zeigler, Adrian Bateman, and
Eliot Graff (Microsoft). Many thanks to Robin Berjon for ReSpec.js.
B. References
B.1 Normative references
[ABNF]
D. Crocker and P. Overell. Augmented BNF for Syntax
Specifications: ABNF. January 2008. Internet RFC 5234. URL:
http://www.ietf.org/rfc/rfc5234.txt
[HTTP11]
R. Fielding; et al. Hypertext Transfer Protocol - HTTP/1.1. June
1999. Internet RFC 2616. URL: http://www.ietf.org/rfc/rfc2616.txt
[NAVIGATOR]
Ian Hickson, David Hyatt. Navigator interface in HTML5. 15 April
2011. Editors' draft. (Work in progress.) URL:
http://dev.w3.org/html5/spec/timers.html#navigator
[RFC2119]
S. Bradner. Key words for use in RFCs to Indicate Requirement
Levels. March 1997. Internet RFC 2119. URL:
http://www.ietf.org/rfc/rfc2119.txt
[RFC4627]
D. Crockford. The application/json Media Type for JavaScript
Object Notation (JSON) July 2006. Internet RFC 4627. URL:
http://www.ietf.org/rfc/rfc4627.txt
[TRACKING-COMPLIANCE]
Justin Brookman; Sean Harvey; Erica Newland; Heather West.
Tracking Compliance and Scope. 13 March 2012. W3C Working Draft.
(Work in progress.) URL:
http://www.w3.org/TR/2012/WD-tracking-compliance-20120313/
[WEBIDL]
Cameron McCormack. Web IDL. 27 September 2011. W3C Working Draft.
(Work in progress.) URL:
http://www.w3.org/TR/2011/WD-WebIDL-20110927/
B.2 Informative references
[COOKIES]
Adam Barth. HTTP State Management Mechanism. April 2011. Internet
Proposed Standard RFC 6265. URL:
http://www.rfc-editor.org/rfc/rfc6265.txt
[KnowPrivacy]
Joshua Gomez; Travis Pinnick; Ashkan Soltani. KnowPrivacy. 1 June
2009. URL:
http://www.knowprivacy.org/report/KnowPrivacy_Final_Report.pdf
[RFC5785]
Mark Nottingham; Eran Hammer-Lahav. Defining Well-Known Uniform
Resource Identifiers (URIs). April 2010. Internet Proposed
Standard RFC 5785. URL: http://www.rfc-editor.org/rfc/rfc5785.txt
[URI-TEMPLATE]
Joe Gregorio; Roy T. Fielding; Marc Hadley; Mark Nottingham; David
Orchard. URI Template. March 2012. Internet RFC 6570. URL:
http://www.rfc-editor.org/rfc/rfc6570.txt
Received on Thursday, 20 September 2012 07:24:37 UTC