The mod_useragent module in Apache is not a standard Apache module. Sometimes people may refer to modules that handle or manipulate user-agent strings as “useragent” modules, but within the standard distribution of the Apache HTTP Server, no module called “mod_useragent” exists.
However, there are several modules related to user agent handling. Examples include mod_rewrite and mod_setenvif. The former lets you create rule-based rewriting of requested URLs, with the user agent string as one possible condition. The latter lets you establish environment variables based on characteristics of the request, including the user agent string. These modules can be used to manipulate the behavior of the server based on the user agent.
