MySQL supports a plugin API that enables creation of server components. Plugins can be loaded at server startup, or loaded and unloaded at runtime without restarting the server. The API is generic and does not specify what plugins can do. The components supported by this interface include, but are not limited to, storage engines, full-text parser plugins, partitioning support, and server extensions.

For example, full-text parser plugins can be used to replace or augment the built-in full-text parser. A plugin can parse text into words using rules that differ from those used by the built-in parser. This can be useful if you need to parse text with characteristics different from those expected by the built-in parser.

The plugin interface is intended as the successor to the older user-defined function (UDF) interface.

The plugin interface uses the plugin table in the mysql database to record information about plugins that have been installed permanently with the INSTALL PLUGIN statement. This table is created as part of the MySQL installation process. Plugins can also be installed for a single server invocation with the --plugin-load option. Plugins installed this way are not recorded in the plugin table. See Section 12.4.3.1, “Installing and Uninstalling Plugins”.

MySQL 5.5.7 and up supports an API for client plugins in addition to that for server plugins. This is used, for example, by authentication plugins where a server-side plugin and a client-side plugin cooperate to enable clients to connect to the server through a variety of authentication methods.