hi MarjaE, you don't need a particular addon in order to avoid animated gifs, as this can be done with built-in preferences in firefox as well: http://kb.mozillazine.org/Animated_images

Tried the about:config fix, it doesn't work, and hasn't worked for years.

it worked fine when i set image.animation_mode to none just when i tested it before...

It isn't working for me. I think it may block certain formats, but not others, and especially not javascript-based animations.

Although blocking specific formats probably wouldn't block javascript anyway.

yes, this only works for moving GIFs

Animation done via JavaScript can only be stopped by blocking that specific script or possibly by hiding specific content via a blocking extension if you visit such pages very often. You would have to learn how you identify this content and what rules to create to block it.

• Nuke Anything Enhanced: https://addons.mozilla.org/firefox/addon/nuke-anything-enhanced/
• Remove It Permanently (RIP): https://addons.mozilla.org/firefox/addon/remove-it-permanently/

You can also stop such an animation by disabling JavaScript on the tab after the page has finished loading.

• Tab Permissions: https://addons.mozilla.org/firefox/addon/tab-permissions/