WordPress.org

Why not reset failed attempts on a successful login?

This is very much by design. Otherwise you could brute force the "admin" password by logging in as your own user every 4th attempt.

What is this option about site connection and reverse proxy?

A reverse proxy is a server in between the site and the Internet (perhaps handling caching or load-balancing). This makes getting the correct client IP to block slightly more complicated.

The option default to NOT being behind a proxy -- which should be by far the common case.

How do I know if my site is behind a reverse proxy?

You probably are not or you would know. We show a pretty good guess on the option page. Set the option using this unless you are sure you know better.

I locked myself out testing this thing, what do I do?

Either wait, or:

If you have ftp / ssh access to the site rename the file "wp-content/plugins/limit-login-attempts/limit-login-attempts.php" to deactivate the plugin.

If you have access to the database (for example through phpMyAdmin) you can clear the limit_login_lockouts option in the wordpress options table. In a default setup this would work: "UPDATE wp_options SET option_value = '' WHERE option_name = 'limit_login_lockouts'"