Apache Module mod_negotiation

Content negotiation, or more accurately content selection, is the selection of the document that best matches the clients capabilities, from one of several available documents. There are two implementations of this.

) which explicitly lists the files containing the variants.Multiviews

), where the server does an implicit filename pattern match, and choose from amongst the results.A type map has a format similar to RFC822 mail headers. It contains document descriptions separated by blank lines, with lines beginning with a hash character ('#') treated as comments. A document description consists of several header records; records may be continued on multiple lines if the continuation lines start with spaces. The leading space will be deleted and the lines concatenated. A header record consists of a keyword name, which always ends in a colon, followed by a value. Whitespace is allowed between the header name and value, and between the tokens of value. The headers allowed are:

directive. This normally includes the encodings x-compress

prefix is ignored for encoding comparisons.Content-Language:

, meaning English. If the variant contains more than one language, they are separated by a comma.Content-Length:

. Common parameters include: level

this defaults to 2, otherwise 0.qs

values are therefore specific to a given resource. Content-Type: image/jpeg; qs=0.8

Content of the page.

Consider, for example, a resource called document.html

which is available in English, French, and German. The files for each of these are called document.html.en

, respectively. The type map file will be called document.html.var

, and will contain the following:

URI: document.html.de

All four of these files should be placed in the same directory, and the .var

in this directory will result in choosing the variant which most closely matches the language preference specified in the user's Accept-Language

is set to "handlers" or "any", a request to MultiviewsMatchdocument.html

and continue negotiating with the explicit type map.

Other configuration directives, such as

can be used to map Aliasdocument.html

, and effectively fakes up a type map which names all those files, assigning them the same media types and content-encodings it would have if the client had asked for one of them by name. It then chooses the best match to the client's requirements, and returns that document.

directive configures whether Apache will consider files that do not have content negotiation meta-information assigned to them when choosing files.MultiviewsMatch

This directive only applies to requests which come from HTTP/1.0 browsers. HTTP/1.1 provides much better control over the caching of negotiated documents, and this directive has no effect in responses to HTTP/1.1 requests.

ForceLanguagePriority None|Prefer|Fallback [Prefer|Fallback]

to serve a one valid result, rather than returning an HTTP result 300 (MULTIPLE CHOICES) when there are several equally valid choices. If the directives below were given, and the user's Accept-Language

each as quality .500

(equally acceptable) then the first matching variant, en

only permitted an es

language response, but such a variant isn't found, then the first variant from the

will be served if more than one variant is acceptable, or first available document will be served if none of the variants matched the client's acceptable list of languages.LanguagePriority

both existed, but the browser did not express a language preference, then foo.html.fr

Note that this directive only has an effect if a 'best' language cannot be determined by any other means or the

. In general, the client determines the language preference, not the server.

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Apache HTTP Server Version 2.4