Module mod_mime

This module associates the request filename's extensions (e.g. .html) with the file's behavior (handlers and filters) and content (mime-type, language, character set and encoding.)

Status: Base
Source File: mod_mime.c
Module Identifier: mime_module

Summary

The directives AddCharset, AddEncoding, AddLanguage and AddType are all used to map file extensions onto the meta-information for that file. Respectively they set the character set, content-encoding, content-language, and MIME-type (content-type) of documents.

In addition, mod_mime may define the "handler" for a document, which controls which module or script will serve the document. With the introduction of "filters" in Apache 2.0, mod_mime can also define the filters that the the content should be processed through (e.g. the Includes output filter for server side scripting) and what filters the client request and POST content should be processed through (the input filters.)

The directives AddHandler, AddOutputFilter, and AddInputFilter control the modules or scripts that serve the document. The MultiviewsMatch directive allows mod_negotiation to consider these file extensions to included when testing Multiviews matches.

The directive TypesConfig is used to specify a file which also maps extensions onto MIME types. Most administrators use the provided mime.types file which associates common filename extensions with IANA registered content types. The current list is maintained at http://www.isi.edu/in-notes/iana/assignments/media-types/media-types although it may be mirrored elsewhere). This simplifies the httpd.conf file by providing the majority of media-type definitions, and they may be overridden by AddType directives as needed.

Please do not send requests to the Apache httpd Project to add any new entries in the distributed mime.types file unless (1) they are already registered with IANA, and (2) they use widely accepted, non-conflicting filename extensions across platforms. category/x-subtype requests will be automatically rejected, as will any new two-letter extensions as they will likely conflict later with the already crowded language and character set namespace.

The core directives ForceType and SetHandler are used to associate all the files in a given container (e.g., <location>, <directory>, or <Files>) with a particular MIME-type or handler. These settings override any filename extension mappings defined in mod_mime.

Note that changing the type or encoding of a file does not change the value of the Last-Modified header. Thus, previously cached copies may still be used by a client or proxy, with the previous headers. If you change the meta-information (language, content type, character set or encoding) you may need to 'touch' affected files (updating their last modified date) to ensure that all visitors are receive the corrected content headers.

Directives

• AddCharset
• AddEncoding
• AddHandler
• AddInputFilter
• AddLanguage
• AddOutputFilter
• AddType
• DefaultLanguage
• MultiviewsMatch
• RemoveCharset
• RemoveEncoding
• RemoveHandler
• RemoveInputFilter
• RemoveLanguage
• RemoveOutputFilter
• RemoveType
• TypesConfig

See also: MimeMagicFile.

Files with Multiple Extensions

Files can have more than one extension, and the order of the extensions is normally irrelevant. For example, if the file welcome.html.fr maps onto content type text/html and language French then the file welcome.fr.html will map onto exactly the same information. If more than one extension is given which maps onto the same type of meta-information, then the one to the right will be used. For example, if ".gif" maps to the MIME-type image/gif and ".html" maps to the MIME-type text/html, then the file welcome.gif.html will be associated with the MIME-type "text/html".

Care should be taken when a file with multiple extensions gets associated with both a MIME-type and a handler. This will usually result in the request being by the module associated with the handler. For example, if the .imap extension is mapped to the handler "imap-file" (from mod_imap) and the .html extension is mapped to the MIME-type "text/html", then the file world.imap.html will be associated with both the "imap-file" handler and "text/html" MIME-type. When it is processed, the "imap-file" handler will be used, and so it will be treated as a mod_imap imagemap file.

Content encoding

A file of a particular MIME type can additionally be encoded a particular way to simplify transmission over the Internet. While this usually will refer to compression, such as gzip, it can also refer to encryption, such a pgp or to an encoding such as UUencoding, which is designed for transmitting a binary file in an ASCII (text) format.

The MIME RFC puts it this way:

The Content-Encoding entity-header field is used as a modifier to the media-type. When present, its value indicates what additional content coding has been applied to the resource, and thus what decoding mechanism must be applied in order to obtain the media-type referenced by the Content-Type header field. The Content-Encoding is primarily used to allow a document to be compressed without losing the identity of its underlying media type.

For example, you may have a file which is a Microsoft Word document, which is pkzipped to reduce its size. If the .doc extension is associated with the Microsoft Word file type, and the .zip extension is associated with the pkzip file encoding, then the file Resume.doc.zipwould be known to be a pkzip'ed Word document.

Apache send a Content-encoding header with the resource, in order to tell the client browser about the encoding method.

Content-encoding: pkzip

Character sets and languages

In addition to file type and the file encoding, another important piece of information is what language a particular document is in, and in what character set the file should be displayed. For example, the document might be written in the Vietnamese alphabet, or in Cyrillic, and should be displayed as such. This information, also, is transmitted in HTTP headers.

The character set, language encoding and mime type are all used in the process of content negotiation (See mod_negotiation) to determine which document to give to the client, when there are alternative documents in more than one character set, language, encoding or mime type. All filename extensions associations created with AddCharset, AddEncoding, AddLanguage and AddType directives (and extensions listed in the MimeMagicFile) participate in this select process. Filename extensions that are only associated using the AddHandler, AddInputFilter or AddOutputFilter directives may be included or excluded from matching by using the MultiviewsMatch directive.

To convey this further information, Apache optionally sends a Content-Language header, to specify the language that the document is in, and can append additional information onto the Content-Type header to indicate the particular character set that should be used to correctly render the information.

Content-Language: en, fr
Content-Type: text/plain; charset=ISO-8859-2

The language specification is the two-letter abbreviation for the language. The charset is the name of the particular character set which should be used.

AddCharset directive

The AddCharset directive maps the given filename extensions to the specified content charset. charset is the MIME charset parameter of filenames containing extension. This mapping is added to any already in force, overriding any mappings that already exist for the same extension.

Example:

    AddLanguage ja .ja
    AddCharset EUC-JP .euc
    AddCharset ISO-2022-JP .jis
    AddCharset SHIFT_JIS .sjis

Then the document xxxx.ja.jis will be treated as being a Japanese document whose charset is ISO-2022-JP (as will the document xxxx.jis.ja). The AddCharset directive is useful for both to inform the client about the character encoding of the document so that the document can be interpreted and displayed appropriately, and for content negotiation, where the server returns one from several documents based on the client's charset preference.

The extension argument is case-insensitive, and can be specified with or without a leading dot.

See also: mod_negotiation

AddEncoding directive

The AddEncoding directive maps the given filename extensions to the specified encoding type. MIME-enc is the MIME encoding to use for documents containing the extension. This mapping is added to any already in force, overriding any mappings that already exist for the same extension. Example:

AddEncoding x-gzip .gz
AddEncoding x-compress .Z

Old clients expect x-gzip and x-compress, however the standard dictates that they're equivalent to gzip and compress respectively. Apache does content encoding comparisons by ignoring any leading x-. When responding with an encoding Apache will use whatever form (i.e., x-foo or foo) the client requested. If the client didn't specifically request a particular form Apache will use the form given by the AddEncoding directive. To make this long story short, you should always use x-gzip and x-compress for these two specific encodings. More recent encodings, such as deflate should be specified without the x-.

The extension argument is case-insensitive, and can be specified with or without a leading dot.

See also: Files with multiple extensions

AddHandler directive

AddHandler maps the filename extensions extension to the handler handler-name. This mapping is added to any already in force, overriding any mappings that already exist for the same extension. For example, to activate CGI scripts with the file extension ".cgi", you might use:

    AddHandler cgi-script .cgi

Once that has been put into your srm.conf or httpd.conf file, any file containing the ".cgi" extension will be treated as a CGI program.

The extension argument is case-insensitive, and can be specified with or without a leading dot.

See also: Files with multiple extensions

AddInputFilter directive

Syntax: AddInputFilter filter[;filter...] extension [extension ...]
Default: none
Context: directory, files, location, .htaccess
Status: mod_mime
Compatibility: AddInputFilter is only available in Apache 2.0.26 and later.

AddInputFilter maps the filename extensions extension to the filter or filters which will process client requests and POST input when they are received by the server. This is in addition to any filters defined elsewhere, including the SetInputFilter directive. This mapping is merged over any already in force, overriding any mappings that already exist for the same extension.

If more than one filter is specified, they must be separated by semicolons in the order in which they should process the content. Both the filter and extension arguments are case-insensitive, and the extension may be specified with or without a leading dot.

See also the Filters documentation.

AddLanguage directive

The AddLanguage directive maps the given filename extension to the specified content language. MIME-lang is the MIME language of filenames containing extension. This mapping is added to any already in force, overriding any mappings that already exist for the same extension.

Example:

AddEncoding x-compress .Z
AddLanguage en .en
AddLanguage fr .fr


Then the document xxxx.en.Z will be treated as being a compressed English document (as will the document xxxx.Z.en). Although the content language is reported to the client, the browser is unlikely to use this information. The AddLanguage directive is more useful for content negotiation, where the server returns one from several documents based on the client's language preference.

If multiple language assignments are made for the same extension, the last one encountered is the one that is used. That is, for the case of:

    AddLanguage en .en
    AddLanguage en-uk .en
    AddLanguage en-us .en

documents with the extension ".en" would be treated as being "en-us".

The extension argument is case-insensitive, and can be specified with or without a leading dot.

See also: Files with multiple extensions, mod_negotiation

AddOutputFilter directive

Syntax: AddOutputFilter filter[;filter...] extension [extension ...]
Default: none
Context: directory, files, location, .htaccess
Status: mod_mime
Compatibility: AddOutputFilter is only available in Apache 2.0.26 and later.

The AddOutputFilter directive maps the filename extensions extension to the filters which will process responses from the server before they are sent to the client. This is in addition to any filters defined elsewhere, including the SetOutputFilter directive. This mapping is merged over any already in force, overriding any mappings that already exist for the same extension.

  AddOutputFilter INCLUDES shtml


If more than one filter is specified, they must be separated by semicolons in the order in which they should process the content. Both the filter and extension arguments are case-insensitive, and the extension may be specified with or without a leading dot.

See also the Filters documentation.

AddType directive

The AddType directive maps the given filename extensions onto the specified content type. MIME-type is the MIME type to use for filenames containing extension. This mapping is added to any already in force, overriding any mappings that already exist for the same extension. This directive can be used to add mappings not listed in the MIME types file (see the TypesConfig directive). Example:

AddType image/gif .gif

Note that, unlike the NCSA httpd, this directive cannot be used to set the type of particular files.

The extension argument is case-insensitive, and can be specified with or without a leading dot.

See also: Files with multiple extensions

MultiviewsMatch directive

MultiviewsMatch permits three different behaviors for mod_negotiation's Multiviews feature. Multiviews allows a request for a file, e.g. index.html, to match any negotiated extensions following the base request, e.g. index.html.en, index.html,fr, or index.html.gz.

The NegotiatedOnly option provides that every extension following the base name must correlate to a recognized mod_mime extension for content negotation, e.g. Charset, Content-Type, Language, or Encoding. This is the strictest implementation with the fewest unexpected side effects, and is the default behavior.

To include extensions associated with Handlers and/or Filters, set the MultiviewsMatch directive to either Handlers, Filters, or both option keywords. If all other factors are equal, the smallest file will be served, e.g. in deciding between index.html.cgi of 500 characters and index.html.pl of 1000 bytes, the .cgi file would win in this example. Users of .asis files might prefer to use the Handler option, if .asis files are associated with the asis-handler.

You may finally allow Any extensions to match, even if mod_mime doesn't recognize the extension. This was the behavior in Apache 1.3, and can cause unpredicatable results, such as serving .old or .bak files the webmaster never expected to be served.

DefaultLanguage directive

The DefaultLanguage directive tells Apache that all files in the directive's scope (e.g., all files covered by the current <Directory> container) that don't have an explicit language extension (such as .fr or .de as configured by AddLanguage) should be considered to be in the specified MIME-lang language. This allows entire directories to be marked as containing Dutch content, for instance, without having to rename each file. Note that unlike using extensions to specify languages, DefaultLanguage can only specify a single language.

If no DefaultLanguage directive is in force, and a file does not have any language extensions as configured by AddLanguage, then that file will be considered to have no language attribute.

See also: Files with multiple extensions, mod_negotiation

RemoveCharset directive

The RemoveCharset directive removes any character set associations for files with the given extensions. This allows .htaccess files in subdirectories to undo any associations inherited from parent directories or the server config files.

The extension argument is case-insensitive, and can be specified with or without a leading dot.

RemoveEncoding directive

The RemoveEncoding directive removes any encoding associations for files with the given extensions. This allows .htaccess files in subdirectories to undo any associations inherited from parent directories or the server config files. An example of its use might be:

/foo/.htaccess:

AddEncoding x-gzip .gz
AddType text/plain .asc
<Files *.gz.asc>
    RemoveEncoding .gz
</Files>

This will cause foo.gz to be marked as being encoded with the gzip method, but foo.gz.asc as an unencoded plaintext file.

Note:RemoveEncoding directives are processed after any AddEncoding directives, so it is possible they may undo the effects of the latter if both occur within the same directory configuration.

The extension argument is case-insensitive, and can be specified with or without a leading dot.

RemoveHandler directive

The RemoveHandler directive removes any handler associations for files with the given extensions. This allows .htaccess files in subdirectories to undo any associations inherited from parent directories or the server config files. An example of its use might be:

/foo/.htaccess:

AddHandler server-parsed .html

/foo/bar/.htaccess:

RemoveHandler .html

This has the effect of returning .html files in the /foo/bar directory to being treated as normal files, rather than as candidates for parsing (see the mod_include module).

The extension argument is case-insensitive, and can be specified with or without a leading dot.

RemoveInputFilter directive

The RemoveInputFilter directive removes any input filter associations for files with the given extensions. This allows .htaccess files in subdirectories to undo any associations inherited from parent directories or the server config files.

The extension argument is case-insensitive, and can be specified with or without a leading dot.

RemoveLanguage directive

The RemoveLanguage directive removes any language associations for files with the given extensions. This allows .htaccess files in subdirectories to undo any associations inherited from parent directories or the server config files.

The extension argument is case-insensitive, and can be specified with or without a leading dot.

RemoveOutputFilter directive

The RemoveOutputFilter directive removes any output filter associations for files with the given extensions. This allows .htaccess files in subdirectories to undo any associations inherited from parent directories or the server config files.

The extension argument is case-insensitive, and can be specified with or without a leading dot.

RemoveType directive

The RemoveType directive removes any MIME type associations for files with the given extensions. This allows .htaccess files in subdirectories to undo any associations inherited from parent directories or the server config files. An example of its use might be:

/foo/.htaccess:

RemoveType .cgi

This will remove any special handling of .cgi files in the /foo/ directory and any beneath it, causing the files to be treated as being of the default type.

Note:RemoveType directives are processed after any AddType directives, so it is possible they may undo the effects of the latter if both occur within the same directory configuration.

The extension argument is case-insensitive, and can be specified with or without a leading dot.

TypesConfig directive

The TypesConfig directive sets the location of the MIME types configuration file. Filename is relative to the ServerRoot. This file sets the default list of mappings from filename extensions to content types; changing this file is not recommended. Use the AddType directive instead. The file contains lines in the format of the arguments to an AddType command:

MIME-type extension extension ...