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Re: The Refresh header is still with us

From: Jeffrey Yasskin <jyasskin@google.com>
Date: Mon, 11 Mar 2019 11:50:18 -0700
Message-ID: <CANh-dX=6fD2vEN4pApFAnPbrP0jUQ_M883r2ThZ=nqF9KZ3H+A@mail.gmail.com>
To: Daniel Stenberg <daniel@haxx.se>
Cc: HTTP Working Group <ietf-http-wg@w3.org>
https://html.spec.whatwg.org/multipage/iana.html tries to register several
things, including this header, with IANA, but most of them haven't made it.
I'm not sure what that pipeline is supposed to look like or where it leaked
in this case. It's probably good to get that registration done at this
point, just to document reality, but with such low usage, someone might be
able to deprecate and remove usage of that header from browsers.

Jeffrey

On Mon, Mar 11, 2019 at 2:32 AM Daniel Stenberg <daniel@haxx.se> wrote:

> Hi friends!
>
> The other day someone filed a bug[1] on curl that we don't support
> redirects
> with the Refresh header. This took me down a rabit hole and I figured I
> would
> share with you what I learned down there.
>
> As you all know, redirects in HTTP is specified to use 3xx response codes
> and
> a Location: header to point out the the URL (I'll use the term URL here
> but
> you know what I mean). This has been the case since RFC 1945 (HTTP/1.0).
> According to an old mail[2] from Roy, Refresh "didn't make it" into that
> spec.
>
> The little detail that it never made it into the 1.0 spec (nor any later
> one)
> doesn't seem to have affected the browsers. Still today, browsers keep
> supporting[3] the Refresh header as a sort of Location: replacement even
> though it seems to never have been present in a HTTP spec.
>
> How frequent is the use of the Refresh header? I decided to make an
> attempt to
> figure out, and for this venture I used the Rapid7 data trove[4]. The
> method
> that data is collected with may not be the best, but it is still 52+
> million
> HTTP responses from different current HTTP servers. (52254873 exactly in
> my
> data dump)
>
> My counts show:
>
>   - Location is used in 18.49% of the responses
>   - Refresh is used in 0.01738% of the responses
>   - Location is thus used 1064 times more often than Refresh
>   - In 35% of the cases when Refresh is used, Location is *also* used
>   - curl thus handles 99.9939% of the redirects in this test
>
> Other random notes:
>
>   - When Refresh is the only redirect header, the response code is usually
> 200
>     (with 404 being the second most)
>   - When both headers are used, the response code is almost always 30x
>   - When both are used, it is common to redirect to the same target and it
> is
>     also common for the Refresh header value to only contain a number (for
>     the number of seconds until "refresh").
>
> Contents:
>
> Redirects can also be done by meta tags and sending the refresh that way,
> but
> I have not investigated how common as that isn't strictly speaking HTTP so
> it
> is outside of my research (and interest) here.
>
> Conclusion:
>
> Nah, sorry, I don't have any. Yet another undocumented quirky corner of
> the
> web I suppose.
>
> [1] = https://github.com/curl/curl/issues/3657
> [2] =
> https://lists.w3.org/Archives/Public/ietf-http-wg-old/1996MayAug/0594.html
> [3] = http://www.otsukare.info/2015/03/26/refresh-http-header
> [4] = https://opendata.rapid7.com/sonar.http/
> [5] =
>
> --
>
>   / daniel.haxx.se
>
>
Received on Monday, 11 March 2019 18:50:53 UTC

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