Was working for me - until Firefox 108.0 when the default Shift-ESC key combination started to be used to open the about:processes tab.
Any suggestions for a good free key combination to use for it going forward?

It's work but it's not automatic(useful for saving data).

A huge sigh of relief to find this! Thank you. -1 star because it would be better as a stop/start toggle. Sometimes it's hard to stop the animation at the right point (need to read it for example).

Can you update this excellent add-on for: Works with firefox 52.0 and later.

Use case:

https://bugzilla.mozilla.org/show_bug.cgi?id=1486332#c9

Version 0.2 is working great on Firefox 52 ESR even though it's marked as requiring Firefox 55 and newer. Stopping JS timer is nice addition to the old version. It would be better if it was marked compatible with 52 so it can be used on current ESR without workarounds.

So happy to have found this rewrite after ToggleGifs (or whatever the name was *bad memory*) wouldn't work with new FF. I'm rating 4 stars only because there doesn't appear to be a way to turn animations back on after you Shift+Esc to turn them off other than reloading the entire page. If that feature could be added (maybe Ctrl+Shift+Esc to reverse), this would be full-on 5 stars for me. Thank you!