First published on December 4, 2008
Update: WordPress 2.8 and up allow case-insensitive login usernames by default. Therefore, you only need the plugin described below if you are using a version older than WordPress 2.8.
In WordPress, if your username is “Peter”, you cannot log in with the username “peter” or “PETER” or any variation with different letter cases. Since usernames in WordPress can only be changed by editing the database, this case-sensitive behaviour is potentially problematic, especially if you run a site where registration is open — you are likely to run into complaints from people who think their password needs to be reset when they’re simply using the wrong case for their username.
While case-sensitive passwords represent an important security feature, the extra security from having case-sensitive usernames might not be worth the potential inconvenience.
Luckily, the WordPress function for login authentication can be overridden. I’ve created a plugin that overrides this function with a very small tweak to accept a case-insensitive username. It should work on WordPress versions 2.5 through 2.7.
To install the plugin, simply unzip the file to the WordPress plugins directory and activate it. Then, a registered user with the username “Peter” can log in with “pEtEr” if they want.