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
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.
See also: MimeMagicFile.
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.
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.By using more than one file extension (see section above about multiple file extensions), you can indicate that a file is of a particular type, and also has a particular encoding.
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
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.
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
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
This will cause filenames containing the .gz extension to be
marked as encoded using the x-gzip encoding, and filenames
containing the .Z extension to be marked as encoded with
x-compress.
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 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
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.
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
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.
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
It is recommended that new MIME types be added using the
AddType directive rather than changing the TypesConfig file.
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 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.
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
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.
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.
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.
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.
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.
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.
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
conf/mime.types
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 ...The extensions are lower-cased. Blank lines, and lines beginning with a hash character (`#') are ignored.