"Before Closing Last Tab" is a Chrome extension developed by mspn. This free tool helps prevent accidental closure of the last active tab in a window by prompting you to confirm if you intend to close it. The extension activates a confirmation dialog only when it detects that you have a single tab remaining in your window, ensuring you don't inadvertently shut down the entire window.

The key feature of this extension is its automatic addition of an event to each page, monitoring whether the tab is the last one within the window, providing a safeguard against unintended tab closures.