This has become one of my favorite and most frequently used Firefox extensions. I often download pictures from the web and it's so annoying when they are in the .webP format hat makes them hard to work with. This extension makes it so easy to download them as jpegs; I just right click and "open image in new tab" and that picture now has the options for the download format. Easy peasy.

As for downloading gifs... while this extension does not do that, it's very easy for anyone to do without an add-on: Click on the gif you want. From the Firefox toolbar at the top select tools --> page info --> media. Scroll down the list and click on the one you want; then click "save as" on the right-hand side.