When you uninstall the Matomo plugin in your WordPress, all data (including all tracked data, reports, and configurations) will be deleted automatically if you use Matomo for WordPress 1.0.7 or newer. You can configure this behaviour by going to “Matomo -> Settings -> Advanced” in your WordPress admin dashboard in case you don’t want to delete any data when you uninstall the plugin.

Alternatively to the UI setting, you can also enforce a specific behaviour by defining a constant in your wp-config.php file:

define('MATOMO_REMOVE_ALL_DATA', true);
// or to never delete data from the database
define('MATOMO_REMOVE_ALL_DATA', false);

You can also manually delete all data

Previous FAQ: I want to extend the WordPress plugin, where is the documentation?