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RewriteRule Flags

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This document discusses the flags which are available to the RewriteRule directive, providing detailed explanations and examples.

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A RewriteRule can have its behavior modified by one or more flags. Flags are included in square brackets at the end of the rule, and multiple flags are separated by commas.

RewriteRule pattern target [Flag1,Flag2,Flag3]

Each flag (with a few exceptions) has a short form, such as CO, as well as a longer form, such as cookie. While it is most common to use the short form, it is recommended that you familiarize yourself with the long form, so that you remember what each flag is supposed to do. Some flags take one or more arguments. Flags are not case sensitive.

Flags that alter metadata associated with the request (T=, H=, E=) have no affect in per-directory and htaccess context, when a substitution (other than '-') is performed during the same round of rewrite processing.

Presented here are each of the available flags, along with an example of how you might use them.


B (escape backreferences)

The [B] flag instructs RewriteRule to escape non-alphanumeric characters before applying the transformation.

In 2.4.26 and later, you can limit the escaping to specific characters in backreferences by listing them: [B=#?;]. Note: The space character can be used in the list of characters to escape, but it cannot be the last character in the list.

mod_rewrite has to unescape URLs before mapping them, so backreferences are unescaped at the time they are applied. Using the B flag, non-alphanumeric characters in backreferences will be escaped. For example, consider the rule:

RewriteRule "^search/(.*)$" "/search.php?term=$1"