• Open Firefox and search for about:config.
  • Right-click in an empty space and go to New String.
  • Name it general.useragent.override and then put this code there:

Mozilla/5.0 (iPhone; CPU iPhone OS 8_3 like Mac OS X) AppleWebKit/600.1.4 (KHTML, like Gecko) FxiOS/1.0 Mobile/12F69 Safari/600.1.4

  • Open a new tab and find the YouTube video you want to download.
  • Start the video and let it play for a few seconds. If there’s an ad, let that finish first.
  • Right-click the video and choose Inspect Element.
  • In the new window that opens, find <div id=”player” and click the arrow to its left to expand it, and then do the same for <div id=”movie_player” below it, and <div class=”html5-video-container” below that.
  • Below that is a long URL following src=”. Double-click that to see the full URL, right-click it, and then choose Copy.
  • Open a new tab in Firefox (or any browser) and enter that into the navigation bar. 
  • Right-click the video in that tab and choose Save Video As.
  • Download videoplayback.mp4 to your computer to save the YouTube video. You can rename it if you want.
  • Return to the tab with the user agent setting, right-click the new string you made, and select Reset to return Firefox to desktop mode.

If inspecting the video page doesn’t show a download link, try the user agent setting in firefox as we did above, and then give it another shot. You might also have luck using a different browser like Chrome or Edge.