Zoom to Fill
This extension will zoom to fill the video in full screen. In other words, remove black bars while watching Youtube in full screen.
What is Zoom to Fill?
Zoom to Fill is a Firefox add-on that allows you to zoom to fill the video in full screen, removing black bars while watching YouTube.
Zoom to Fill is risky to use as it requires a number of sensitive permissions that can potentially harm your browser and steal your data. Exercise caution when installing this add-on. Review carefully before installing. We recommend that you only install Zoom to Fill if you trust the publisher.
Zoom to Fill has earned a fairly good reputation and likely can be trusted.