Firefox does not include the patented components needed to play MP4/H.264 encoded files.

On Windows Vista and later, these functions are provided by Microsoft Media Foundation.

I think on Linux you need the ffmpeg package installed (outside of Firefox) for Firefox to decode MP4/H.264 video. However, that's just based on a quick web search; I don't have personal experience one way or the other.

Why such an old version of Firefox??

You can test at say https://www.youtube.com/html5/ as all checks should be blue.

If a couple are red then you may not have the appropriate FFmpeg package installed as mentioned. This package among some other packages may not get installed in a new Linux distro install due to legal or copyright reasons. Ubuntu for example has a Ubuntu Restricted Extras for this.

Firefox 61.0.1 Release and 60.1.0 ESR are the current versions.

jscher2000 said

Why such an old version of Firefox??

Thank you for your reply.

Actually my firefox which this question is about is not old. It is the latest available for RHEL-6.10. I think it must be version 61 or close to it. But I sent the message from a browser at work, where I'm still running Linux5. So please pay no attention to version 45, which was automatically extracted by the website. If this important, I can verify the actual version when I go home tonite.

Note that Firefox 45 still supports gstreamer (gstreamer support was removed in Firefox 46; Bug 1234092).

• media.gstreamer.enabled
• media.ffmpeg.enabled

James said

You can test at say https://www.youtube.com/html5/ as all checks should be blue. If a couple are red then you may not have the appropriate FFmpeg package installed as mentioned. This package among some other packages may not get installed in a new Linux distro install due to legal or copyright reasons. Ubuntu for example has a Ubuntu Restricted Extras for this. Firefox 61.0.1 Release and 60.1.0 ESR are the current versions.

Thank you for your help. I will try it as soon as I get back home tonight.

Actually my firefox which this question is about is not old. It is the latest available for RHEL-6.10. But I asked the question from a browser at work, where I'm still running Linux5. So please pay no attention to version 45, which was automatically extracted by the website.

Hmm right Firefox 45.0 and earlier still used Gstreamer.

Firefox 46.0 and later requires GTK 3.4 (three.four) though more Linux distros in last few years (that are not about long term stability support with older branches) should have say GTK 3.12 or later by now. This also means Firefox will not be themed by GTK 2 Themes anymore and will looked unthemed with missing scrollbar arrows if a GTK2 theme is in use instead of GTK3.

fermion said

Thank you for your help. I will try it as soon as I get back home tonight. Actually my firefox which this question is about is not old. It is the latest available for RHEL-6.10.

For the company Mozilla it is old and EOL as Firefox 45.9.0 ESR released back on April 19, 2017 was the last minor update for security and allowed stability fixes. https://www.mozilla.org/firefox/releases/

Even the legacy Firefox 52 ESR (52.9.0esr is current) is almost EOL as it will get no more updates for security and or stability fixes after Sept 5 when 62.0 Release and 60.2.0esr are Released.