Apache provides a convenient way to conditionally check for its version number, which can be useful when writing directives that require specific modules and configurations. This tutorial explains how it’s done with a few simple examples.

Thanks to Apache’s version module, mod_version, we conditionally may check Apache’s current version number. This module is available in Apache 2.0.56 and later.

Currently the only directive included in mod_version is <IfVersion>, which may be included via the server configuration file, virtual host, directory, or .htaccess. So it’s a pretty straightforward module to learn. Let’s look at some examples of <IfVersion> to see how it works.

Examples

Greater than or equal to a specific version of Apache:

<IfVersion >= 2.4>
	# do stuff for Apache greater than or equal to version 2.4.0
</IfVersion>

Less than specific Apache version:

<IfVersion < 2.3>
	# do stuff for Apache less than version 2.3.0
</IfVersion>

Using a regular expression to match specific version numbers:

<IfVersion = /^2.4.[01234]$/>
	# matches versions 2.4.0, 2.4.1, 2.4.2, 2.4.3, 2.4.4
</IfVersion>

Instead of forward-slashing the regex as in the previous example, we can replace the slashes with a tilde ~:

<IfVersion !~ ^2.4.[01234]$>
	# matches any version that is NOT 2.4.0, 2.4.1, 2.4.2, 2.4.3, 2.4.4
</IfVersion>

Notice here that we are negating the regular expression by prefixing it with an exclamation point !. Also note that if the operator is omitted, it’s assumed to be “equals” =. You can get more details in the Apache documentation.