Introduction
The about:config is an advanced Firefox tool that allows you to adjust internal browser settings. With it, you can customize features, improve performance, or change default behaviors. Use it carefully, as incorrect changes may affect the stability of the browser.
Let's get started!
1 - Without further ado, to block the automatic playback of GIFs in Firefox, type about:config in the browser's address bar and press Enter ↲.
2 - A security warning will be displayed, alerting you about the advanced settings. As mentioned earlier, these changes should be made with caution. Click on – after all, we know what we're doing, right? :-)
3 - In the search field at the top of the page, type: image.animation_mode. The corresponding option will appear, with the default value set to normal.
4 - Double-click on the entry (or use the "Edit" button) and change the value to none.
Done! Now you can browse without distractions caused by animated GIFs. Check in the image below if your settings are correct.