What is the RewriteCond rule in Apache htaccess?

2 years ago
Isabella Edwards
2 minutes

In the .htaccess file of Apache, RewriteCond rules are used to define conditions for rewrite rules. This allows you to use conditions to limit the scope of rewrite rules.

The syntax for RewriteCond is as follows:

RewriteCond TestString CondPattern [flags]
  1. TestString: The string to be tested, usually obtained from the requested URL. You can define TestString using variables, pattern matching, or other conditions.
  2. CondPattern: a pattern used for conditional matching. It can be a regular expression, string, or similar.
  3. Flags (optional): You can add some marks to modify the behavior of the rules, such as NC (case-insensitive), L (stop processing subsequent rules), etc.

Here are some common usage examples:

  1. Match the conditions to the HTTP request headers.
RewriteCond %{HTTP_USER_AGENT} GoogBot [NC]

This will match when “GoogBot” is included in the user agent string.

  1. Match the URL to the conditions and requirements.
RewriteCond %{REQUEST_URI} ^/admin

This will match when the requested URL starts with “/admin”.

  1. The host name requested must match the conditions for use.
RewriteCond %{HTTP_HOST} ^example\.com$

This will match when the requested hostname is “example.com”.

  1. Match the query string with the conditions for use.
RewriteCond %{QUERY_STRING} ^id=123$

This will match when the requested query string is “id=123”.

It is important to note that RewriteCond rules will only take effect when they are matched with subsequent RewriteRule rules. If there are no subsequent RewriteRule rules, the RewriteCond rules will not work.

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