As for Firefox, I found the following statement on Howtogeek:
Firefox offers a built-in way to stop animated GIFs from playing, or to force them to only play once.
To change this setting, type about:config into Firefox’s address bar and press Enter. You’ll see a warning telling you to be careful here, as you could change settings you shouldn’t. Be careful on this screen and don’t change any settings unless you know what you’re doing. Click “I’ll be careful, I promise!” to agree you’ve understood the warning.
Type image.animation into the search box on the about:config page. You’ll see a setting named image.animation_mode , which is set to normal by default. The “normal” behavior is to play every animated image on repeat over and over again.
Double-click the setting and set it to none to stop animated GIFs from playing. You could also set it to once if you want each animated GIF to play only once instead of repeating over and over. You don’t have to restart Firefox after making this change.
Opera:Can use extension Animation Policy
Block GIF images in Opera:
1. Press F12 Key located on top of the keyboard.
2. Uncheck the option : “Enable GIF/SVG animation” .
3. And you are done!