.htaccess files (or "distributed configuration files")
provide a way to make configuration changes on a per-directory basis. A
file, containing one or more configuration directives, is placed in a
particular document directory, and the directives apply to that
directory, and all subdirectories thereof.
Note: If you want to call your
.htaccess file something
else, you can change the name of the file using the
directive. For example, if you would rather call the file
.config then you can put the following in your server
What you can put in these files is determined by the
directive. This directive specifies, in categories, what directives
will be honored if they are found in a
.htaccess file. If
a directive is permitted in a
.htaccess file, the
documentation for that directive will contain an Override section,
specifying what value must be in
AllowOverride in order
for that directive to be permitted.
For example, if you look at the documentation for the AddDefaultCharset
directive, you will find that it is permitted in
files. (See the Context line in the directive summary.) The Override line reads
FileInfo". Thus, you must have at least
AllowOverride FileInfo" in order for this directive to be
If you are unsure whether a particular directive is permitted in a
.htaccess file, look at the documentation for that
directive, and check the Context line for ".htaccess."
In general, you should never use
.htaccess files unless
you don't have access to the main server configuration file. There is,
for example, a prevailing misconception that user authentication should
always be done in
.htaccess files. This is simply not the
case. You can put user authentication configurations in the main server
configuration, and this is, in fact, the preferred way to do
.htaccess files should be used in a case where the
content providers need to make configuration changes to the server on a
per-directory basis, but do not have root access on the server system.
In the event that the server administrator is not willing to make
frequent configuration changes, it might be desirable to permit
individual users to make these changes in
for themselves. This is particularly true, for example, in cases where
ISPs are hosting multiple user sites on a single machine, and want
their users to be able to alter their configuration.
However, in general, use of
.htaccess files should be
avoided when possible. Any configuration that you would consider
putting in a
.htaccess file, can just as effectively be
made in a <Directory>
section in your main server configuration file.
There are two main reasons to avoid the use of
The first of these is performance. When
is set to allow the use of
.htaccess files, Apache will
look in every directory for
.htaccess files. Thus,
.htaccess files causes a performance hit,
whether or not you actually even use them! Also, the
.htaccess file is loaded every time a document is
Further note that Apache must look for
in all higher-level directories, in order to have a full complement of
directives that it must apply. (See section on how
directives are applied.) Thus, if a file is requested out of a
/www/htdocs/example, Apache must look for the
And so, for each file access out of that directory, there are 4 additional file-system accesses, even if none of those files are present. (Note that this would only be the case if .htaccess files were enabled for /, which is not usually the case.)
The second consideration is one of security. You are permitting users to modify server configuration, which may result in changes over which you have no control. Carefully consider whether you want to give your users this privilege.
Note that it is completely equivalent to put a .htaccess file in a
/www/htdocs/example containing a directive, and
to put that same directive in a Directory section
/www/htdocs/example> in your main server configuration:
.htaccess file in
AddType text/example .exm
AddType text/example .exm
However, putting this configuration in your server configuration file will result in less of a performance hit, as the configuration is loaded once when Apache starts, rather than every time a file is requested.
The use of
.htaccess files can be disabled completely
by setting the
AllowOverride directive to "none"
The configuration directives found in a
are applied to the directory in which the
is found, and to all subdirectories thereof. However, it is important
to also remember that there may have been
in directories higher up. Directives are applied in the order that they
are found. Therefore, a
.htaccess file in a particular
directory may override directives found in
found higher up in the directory tree. And those, in turn, may have
overridden directives found yet higher up, or in the main server
configuration file itself.
In the directory
/www/htdocs/example1 we have a
.htaccess file containing the following:
(Note: you must have "
AllowOverride Options" in effect
to permit the use of the "
Options" directive in
In the directory
/www/htdocs/example1/example2 we have
.htaccess file containing:
Because of this second
.htaccess file, in the directory
/www/htdocs/example1/example2, CGI execution is not
permitted, as only
Options Includes is in effect, which
completely overrides any earlier setting that may have been in
If you jumped directly to this part of the document to find out how
to do authentication, it is important to note one thing. There is a
common misconception that you are required to use
.htaccess files in order to implement password
authentication. This is not the case. Putting authentication directives
<Directory> section, in your main server
configuration file, is the preferred way to implement this, and
.htaccess files should be used only if you don't have
access to the main server configuration file. See above for a
discussion of when you should and should not use
Having said that, if you still think you need to use a
.htaccess file, you may find that a configuration such as
what follows may work for you.
You must have "
AllowOverride AuthConfig" in effect for
these directives to be honored.
.htaccess file contents:
AuthName "Password Required"
Require Group admins
AllowOverride AuthConfig must be in effect
for these directives to have any effect.
Please see the authentication tutorial for a more complete discussion of authentication and authorization.
Another common use of
.htaccess files is to enable
Server Side Includes for a particular directory. This may be done with
the following configuration directives, placed in a
.htaccess file in the desired directory:
AddType text/html shtml
AddHandler server-parsed shtml
AllowOverride Options and
FileInfo must both be in effect for these directives to have any
Please see the SSI tutorial for a more complete discussion of server-side includes.
Finally, you may wish to use a
.htaccess file to permit
the execution of CGI programs in a particular directory. This may be
implemented with the following configuration:
AddHandler cgi-script cgi pl
Alternately, if you wish to have all files in the given directory be considered to be CGI programs, this may be done with the following configuration:
AllowOverride Options must be in effect for
these directives to have any effect.
Please see the CGI tutorial for a more complete discussion of CGI programming and configuration.
When you put configuration directives in a
file, and you don't get the desired effect, there are a number of
things that may be going wrong.
Most commonly, the problem is that
AllowOverride is not
set such that your configuration directives are being honored. Make
sure that you don't have a
AllowOverride None in effect
for the file scope in question. A good test for this is to put garbage
.htaccess file and reload. If a server error is
not generated, then you almost certainly have
None in effect.
If, on the other hand, you are getting server errors when trying to access documents, check your Apache error log. It will likely tell you that the directive used in your .htaccess file is not permitted. Alternately, it may tell you that you had a syntax error, which you will then need to fix.