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Apache HTTP Server Version 2.0
Apache Module mod_mime
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Summary
This module is used to associate various bits of "meta
information" with files by their filename extensions. This
information relates the filename of the document to it's
mime-type, language, character set and encoding. This
information is sent to the browser, and participates in content
negotiation, so the user's preferences are respected when
choosing one of several possible files to serve. See
mod_negotiation for more information
about content negotiation.
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. The directive TypesConfig is used to specify a
file which also maps extensions onto MIME types.
In addition, mod_mime may define the handler and filters that originate and process
content. 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 be included when testing Multiviews matches.
While mod_mime associates meta-information
with filename extensions, the core server
provides directives that are used to associate all the files in a
given container (e.g., <location>, <directory>, or <Files>) with particular
meta-information. These directives include ForceType, SetHandler, SetInputFilter, and SetOutputFilter. The core directives
override any filename extension mappings defined in
mod_mime.
Note that changing the meta-information for 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
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.
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
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.
Charset
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
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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
AddEncoding Directive
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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.
AddHandler Directive
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Files having the name extension will be served by the
specified 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
AddInputFilter Directive
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AddInputFilter maps the filename extensions extension to the 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.
AddLanguage Directive
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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
AddOutputFilter Directive
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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.
For example, the following configuration will process all
.shtml files for server-side includes and will then compress
the output using mod_deflate.
AddOutputFilter INCLUDES;DEFLATE 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
AddType Directive
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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 TypesConfigfile.
The extension argument is case-insensitive, and can be specified with or without a leading dot.
See also
DefaultLanguage Directive
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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.
Example
DeafaultLanguage en
See also
MultiviewsMatch Directive
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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.
For example, the following configuration will allow handlers and filters to participate in Multviews, but will exclude unknown files:
MultiviewsMatch Handlers Filters
See also
RemoveCharset Directive
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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.
Example
RemoveCharset .html .shtml
RemoveEncoding Directive
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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
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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
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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
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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
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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.
Example
RemoveOutputFilter shtml
See also
RemoveType Directive
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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: RemoveTypedirectives are processed after anyAddTypedirectives, 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
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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. 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. This
simplifies the httpd.conf file by providing the
majority of media-type definitions, and may be overridden by
AddType directives as
needed. You should not edit the mime.types file,
because it may be replaced when you upgrade your server.
The file contains lines in the format of the arguments to
an AddType directive:
MIME-type extension extension ...
The case of the extension does not matter. Blank lines, and lines beginning with a hash character (`#') are ignored.
Please do not send requests to the Apache HTTP Server 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.
See also
