Hi

Thank you for your question, hopefully I can help.

If you want to use and test a pre-Release version of Firefox, you can download Firefox Beta, Firefox Developer Edition or Firefox Nightly.

• Firefox Beta is the version before the live version and has the latest features in a more stable environment. You can download it from here.

• Firefox Developer Edition is the version before Firefox Beta and also comes with extra tools for web developers. You can download it from here. (I personally use this version as my main web browser.)

• Firefox Nightly is a very rough, first draft version that is very much a work in progress and updates...nightly(!). If you really want to give this a try, you can download it from here, although I recommend you do not use this as your main browser due to issues you may experience.

Regardless of the version you are using, you can help support Firefox by turning on Telemetry. These are options that sending performance and usage data straight to our engineers so that they can see how to make Firefox better. You can read how to turn this on here.

Thanks to the information that you have supplied, I can see that you are using the latest version of Firefox, so you should be able to view that video file. If the video still does not play, it would be useful to know whether it is just this particular video, or does the same problem occur with other Facebook videos.

I hope this helps, but if not, please come back here and we can look into a different solution for you. Thank you for your interest in Firefox and for wanting to get involved in testing earlier versions.

Firefox 42.0 is the latest as it was released on Nov 3.

May not help that you appear to be using WinXP and have a few Flash Player Plugins installed on system.

Shockwave Flash 19.0 r0 Shockwave Flash 18.0 r0 Shockwave Flash 17.0 r0

Download the Flash Player 19.0.0.245 or 18.0.0.261 ESR (plugin based) https://www.adobe.com/products/flashplayer/distribution3.html

Then shut down Firefox and uninstall the (plugin based) Flash Players and then install Firefox player you downloaded. https://helpx.adobe.com/flash-player/kb/uninstall-flash-player-windows.html

Release < Beta (b#) < Aurora (a2) (aka Developer Edition) < Nightly (a1)

There are usually six to twelve builds on Beta channel for a version. The Aurora and Nightly get checkins usually everyday so it gets updates each of those days. This means there can be issues until fixed, finished or reverted.