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YouTube videos will not start playing

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For a few weeks now, I cannot start a You Tube clip using my favourite browser Firefox. When I select a clip, it displays with a rather blurred image. When I click on the red arrow to start the clip, nothing happens. Video clips from sites other than You Tube work fine. I tried opening a clip using Microsoft Edge and it worked fine. I am using Windows 10 64 bit and the Firefox is version 78.0.2. Any suggestions as to how to fix this?

For a few weeks now, I cannot start a You Tube clip using my favourite browser Firefox. When I select a clip, it displays with a rather blurred image. When I click on the red arrow to start the clip, nothing happens. Video clips from sites other than You Tube work fine. I tried opening a clip using Microsoft Edge and it worked fine. I am using Windows 10 64 bit and the Firefox is version 78.0.2. Any suggestions as to how to fix this?

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You can try these steps in case of issues with web pages:

You can reload web page(s) and bypass the cache to refresh possibly outdated or corrupted files.

  • hold down the Shift key and left-click the Reload button
  • press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux)
  • press "Command + Shift + R" (Mac)

Clear the Cache and remove the Cookies for websites that cause problems via the "3-bar" Firefox menu button (Options/Preferences).

"Remove the Cookies" for websites that cause problems:

  • Options/Preferences -> Privacy & Security
    Cookies and Site Data: "Manage Data"

"Clear the Cache":

  • Options/Preferences -> Privacy & Security
    Cookies and Site Data -> Clear Data -> Cached Web Content: Clear

Start Firefox in Safe Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration is causing the problem.

  • switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Themes
  • do NOT click the "Refresh Firefox" button on the Safe Mode start window

You can remove all data stored in Firefox for a specific domain via "Forget About This Site" in the right-click context menu of an history entry ("History -> Show All History" or "View -> Sidebar -> History").

Using "Forget About This Site" will remove all data stored in Firefox for this domain like history and cookies and passwords and exceptions and cache, so be cautious. If you have a password or other data for that domain that you do not want to lose then make sure to backup this data or make a note.

You can't recover from this 'forget' unless you have a backup of involved files.

If you revisit a 'forgotten' website then data for that website will be saved once again.