MP4NoMore is a free Chrome extension developed by mtomasek. It falls under the category of Browsers and specifically belongs to the Add-ons & Tools subcategory. This extension aims to address the problem faced by Vivaldi and Chrome on Late Model Macs, where they are unable to play MP4 videos.

The extension works by instructing websites to stop offering MP4 as a playback option. While it does help in mitigating the issue, it does not completely fix the problem with Vivaldi. Users may still encounter the error message "The media could not be played" on some sites.

It is important to note that if a website only offers MP4 videos and this extension is unable to serve MP4 due to the underlying issue, users will still encounter the aforementioned error message. This has been observed with certain Twitter videos, for example.