Language on the Web

Content authors need to know how to declare the language of a document or range of text in the Web technology they are dealing with. Most XML-based formats, such as XHTML, SVG, SSML, etc. will make use of the xml:lang attribute defined by the XML specification, but there may be other markup, such as the lang attribute in HTML.

Content authors should consider whether you need to make a difference between declaring the language of a document or range of text so that tools can process it, and declaring the intended audience of a resource (ie. metadata). You may need to apply slightly different approaches for these in (X)HTML, for example. You should also avoid confusing language declarations with script and character encoding declarations.

Content authors and webmasters also need to know how to use values for languages in a standard way. The current standard approach for W3C specifications is to use the rules expressed in BCP 47. This replaces earlier specifications such as RFC 3066 and RFC 1766, and goes beyond information available in the ISO language and country standards. You should also use the IANA Language Subtag Registry to look up language tags, rather than the ISO specifications.

Web masters or people working with server settings may also need to set up the server so that it sends language-related HTTP information with requested files. This is typically done as part of content-negotiation, where the server sends the user one of several alternative versions of a document depending on the settings of the users browser.

When an HTTP request is made to a server, the requesting user agent usually sends information about language preferences. The server can then use this information to return a version of the document in the appropriate language if such an alternative is available.

End-users should know how to check that their language preferences are correctly set, and how to change them if not.

Webmasters should know how to set up their server to manage language-based content negotiation.

Web designers and developers dealing with multilingual sites should consider how to guide visitors to the right resources.

On most browsers, you can use CSS selectors to apply different styling according to the language of a range of text. For example, within an English document you can assign embedded Thai text a particular font and appropriate line height adjustments anywhere it appears, just by the fact that the content is labeled as Thai.

In CSS, style sheet developers can use selectors with the content property, where it is supported, to automatically indicate the language of a link target.

Schema or specification developers should consider whether the format they are developing includes markup to enable authors to identify the document's main language and any changes in language within the document.

Schema or specification developers should also be clear when it is appropriate to use xml:lang in XML-based formats, and when they should create a different attribute or element to specify language information.