.htaccess

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.htaccess (Hypertext Access) is the default name of Apache's directory-level configuration file. It provides the ability to customize configuration directives defined in the main configuration file. The configuration directives need to be in .htaccess context and the user needs appropriate permissions.

Common usage

Custom Error Pages

ErrorDocument 404 my404page.html
This code can be used to create any custom page. Certain pages are more complicated to modify — if you create a custom 404 Forbidden page, then a viewer will not see the custom page. Here is an example showing a method used to get around this:
ErrorDocument 404 /public/my404page.html
In this case you would need another .htaccess file in /public, containing these lines:
Order allow,deny
Allow from all

Password protection

Make the user enter a name and password before viewing a directory. 

AuthUserFile /home/newuser/www/stash/.htpasswd
AuthGroupFile /dev/null
AuthName "Protected Directory"
AuthType Basic
<Limit GET POST>
require user newuser
</Limit>

Now run this command to create a new password for the user 'newuser'. 

htpasswd /home/newuser/www/stash/.htpasswd newuser

Password unprotection

Unprotect a directory inside an otherwise protected structure: 

Satisfy any

Enable Server Side Includes (SSI)

AddType text/html .shtml
AddHandler server-parsed .shtml
Options Indexes FollowSymLinks Includes

Deny users by IP address

Order allow,deny
Deny from 123.45.67.8
Deny from 123.123.7
Allow from all
This would ban anyone with an IP address of 123.45.67.8 and would also ban anyone with an IP address starting in 123.123.7: for example, 123.123.74.42 would not gain access.

Change the default directory page

DirectoryIndex homepage.html
Here, anyone visiting http://www.example.com/ would see the homepage.html page, rather than the default index.html.

Redirects

Redirect page1.html page2.html
If someone was to visit http://www.example.com/page1.html, they would be sent (with an HTTP status code of 302) to http://www.example.com/page2.html.

Prevent hotlinking of images

The following .htaccess rules use mod rewrite.

From specific domains

RewriteEngine on
RewriteCond %{HTTP_REFERER} ^http://([^/]+\.)?baddomain1\.com [NC,OR]
RewriteCond %{HTTP_REFERER} ^http://([^/]+\.)?baddomain2\.com [NC,OR]
RewriteCond %{HTTP_REFERER} ^http://([^/]+\.)?baddomain3\.com [NC]
RewriteRule \.(gif|jpg)$ http://www.example.com/hotlink.gif [R,L]

Except from specific domains

RewriteEngine on
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http://(www\.)?example.com/.*$ [NC]
RewriteRule \.(gif|jpg)$ http://www.example.com/hotlink.gif [R,L]
Unless the image is displayed on example.com, browers would see the image hotlink.gif.

Note: Hotlink protection using .htaccess relies on the client sending the correct "Referer" value in the http GET request. Programs such as Windows Media Player send a blank referrer, so that attempts to use .htaccess to protect movie files for example are ineffective.

Standardise web address

RewriteEngine on

RewriteCond %{HTTP_HOST} ^example.com$
RewriteRule (.*) http://www.example.com/$1 [R=Permanent]

If anyone types in your sites address without the 'www' prefix, this will redirect them to the page with the 'www' prefix

  • Permanent address change: suppose your site has permanently moved to a new domain. The following rules apply said changes:
RewriteCond %{HTTP_HOST} ^www.domain.com$ [NC]
RewriteRule  ^(.*)$ http://www.domain2.com/$1  [R=301, L]

Here "[NC]" means case insensitive and its called "RewriteCond Flags". [R=301] means "moved permanently". It is called a redirection header code.

Dynamic vs. static URLs

Old dynamic URL format: 

/index\.php?product=auto&make=bmw&year=2007

New static URL format: 

/product/auto/bmw/2007

Mod_rewrite code for use in .htaccess file: 

# Enable mod_rewrite, start rewrite engine
Options +FollowSymLinks
RewriteEngine on
#
# Internally rewrite search engine friendly static URL to dynamic filepath and query
RewriteRule ^product/([^/]+)/([^/]+)/([^/]+)/?$ /index.php?product=$1&make=$2&year=$3 [L]
#
# Externally redirect client requests for old dynamic URLs to equivalent new static  URLs
RewriteCond %{THE_REQUEST} ^[A-Z]{3,9}\ /index\.php\?product=([^&]+)&make=([^&]+)&year=([^\ ]+)\ HTTP/
RewriteRule ^index\.php$ http://example.com/product/%1/%2/%3? [R=301,L]

Nice looking URLs (no querying) with pagination

Suppose your URL is: 

domain.com/article.php?name=title&page=5

And you want to change it to: 

domain.com/articles/title/5/

Add the following to your .htaccess file: 

RewriteRule ^articles/(A-Za-z0-9-]+)/([0-9]+)/?$ article.php?name=$1&page=$2 [L]

The rule is defined in the regular expression. The "[L]" means "Last Rule" and it is called "RewriteRule Flags".

Directory rules

A .htaccess file controls the directory it is in, plus all subdirectories. However, by placing additional .htaccess files in the subdirectories, this can be overruled.

User permissions

The user permissions for .htaccess are controlled on server level with the AllowOverride directive which is documented in the Apache Server Documentation.

Other uses

Some web developers have modified .htaccess to perform custom tasks server-side before serving content to the browser. Developer Shaun Inman shows it is possible to edit .htaccess to allow for Server Side Constants within CSS.

See also

External links

Apache.org

Other

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