I found this great list of clever things you can do with WordPress’ config file:

Many WordPress users know the wp-config.php file as the key to the WordPress database. It is where you set the database name, username, password, and location. [...] But what many users don’t know is that the wp-config.php file may be used to specify a wide variety of configurational settings, enabling you to improve the functionality, performance, and security of your WordPress-powered site.

via WordPress Configuration Tricks.

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