Usually the video player controls have a button for full screen. Possibly a context menu might also have it (right-click or Ctrl+click on the player). Do either of those work with the videos you're viewing?

Thank you much for the reply. When I select the expansion icon at the lower right of the video screen, which would normally change the video to full screen as it has always done, nothing happens. Doing the same with either left or right click of the mouse buttons has the same response - nothing.

When you right-click the player, do you get a plugin menu (e.g., the short menu shown by the Flash player) or Firefox's menu?

For Firefox's native video player, prior to Firefox 42, sites could be denied permission to use full screen. That permission approach was removed, so hopefully the removal of all references to the fullscreen permission in the user interface won't be a problem.

Could you test in Firefox's Safe Mode? In Safe Mode, Firefox temporarily deactivates extensions, hardware acceleration, and some other advanced features to help you assess whether these are causing the problem.

If Firefox is not running: Hold down the option key when starting Firefox.

If Firefox is running: You can restart Firefox in Safe Mode using either:

• "3-bar" menu button > "?" button > Restart with Add-ons Disabled
• Help menu > Restart with Add-ons Disabled

and OK the restart.

Both scenarios: A small dialog should appear. Click "Start in Safe Mode" (not Refresh).

Any improvement? (More info: Diagnose Firefox issues using Troubleshoot Mode)

Does nothing. Same scenario in safe mode. clicking left or right mouse buttons on expansion icon or on the video screen itself does nothing either way - regular or safe mode.

Hmm, it's unusual not to get any right-click or Ctrl+click context menu on a video player. Does this occur on all sites with video players or only on particular sites? Could you post a link directly to a page where the full screen and right-click are not working?

http://www.tvids.net/watch442/Nashville/season-04-episode-01-Cant-Let-Go

It has always worked before. Not sure what the difference is at this point. Youtube would not go to full screen either, but their instructions for resolution of the issue were easy to follow and so full screen use was restored - just on Youtube.

That video is played in an iframe. This iframe doesn't have the allowfullscreen="true" attribute that is required to be able to switch to Full Screen mode. If I add this attribute and reload the iframe then the Full Screen mode button works for me.

You can try to contact the website and ask them to look into this omission that is required for current Firefox releases with the HTML5 media player.

See:

• http://blog.pearce.org.nz/2011/11/firefoxs-html-full-screen-api-enabled.html

Shouldn't a web browser be easy to use? Does the average consumer need to know code to use your product? Really? It should be very user friendly. Click an icon and there you go. Or do a drop down menu on settings, select allow video full screen and there you go. Seriously?

There are five other browsers I can use. Thanks for the effort, but not a good solution.

Anyone on your team know how this thing works? It was not a problem for the last year. Unless there was an update or some bug introduction recently, the solution should be simple. Just a thought.

Security gets tighter and tighter with each Firefox release, so websites may have to modify their coding to adapt to such changes.

Also the website may have been using the Flash plugin in previous Firefox version and has switched to supporting the HTML5 media player.

You can contact a website that doesn't work properly and to inform them about your issue and kindly ask them to look into this and point them to this blog page.

• http://blog.pearce.org.nz/2011/11/firefoxs-html-full-screen-api-enabled.html