This setting is found under Security | HTTP security. If you enable this setting but your server doesn't have HTTPS enabled for your site, you will be locked out of your site. Moodle will require you to use HTTPS when you log in, but you won't be able to comply. If that happens to you, you must go into the Moodle database and change this setting to No.
The following screenshot shows an administrator using the web-based product phpMyAdmin to edit this setting in Moodle's database. Note the setting for logging in via HTTPS is in the mdl_config table. The administrator is clicking on the edit icon. If this cell contains a 0, HTTPS login is not required. If it contains a 1, HTTPS login is required. If you're locked out ...
