mSession Keeper is a free Firefox add-on designed for web developers and users who want to maintain active sessions on their favorite websites without constant refreshes. This tool allows users to set up session management by defining three specific URLs: a Start URL, a Stop URL, and a session URL that will be pinged in the background. Once these URLs are configured, the add-on automatically handles the session maintenance, ensuring that users remain logged in without manual intervention.

The user interface is straightforward, allowing for easy entry of the required URLs and a simple process to save sessions. Upon saving, users can see a list of their saved sessions at the top of the interface. This functionality is particularly useful for developers who need to keep sessions active while testing web applications, making mSession Keeper a valuable addition to any web development toolkit.