M2 FPC Monitor is a free Chrome add-on developed by Craig Newbury. It falls under the category of Browsers and specifically the subcategory of Add-ons & Tools. This program aims to provide users with the ability to easily identify whether a page on a Magento 2 website was served by the full page cache (FPC) or not.

The main feature of M2 FPC Monitor is its at-a-glance display, which shows users if a Magento 2 page was served via the full page cache. This is done by monitoring the "x-magento-cache-debug" HTTP header. With this information, users can quickly determine if a page was served by the FPC, which can be useful for troubleshooting and optimization purposes.

Overall, M2 FPC Monitor is a handy tool for Magento 2 website owners or developers who want to easily identify whether their pages are being served by the full page cache. Its simple and straightforward interface makes it accessible to users of all levels of technical expertise.