Disabling webp in Firefox

If you're one of the weird persons who dislike new features, this short article could be useful for you.

A few years ago Google invented webp, a new image compression for web. It was proclaimed as better than jpeg or png and supporting both lossy and lossless compression. The majority of browsers (including Firefox since version 65) support this new format. Of course, it is fine -- better compression, less traffic, faster page loading, less lose of money. But! If you'd like to save a picture from web (either jpeg or png), you can't do this, as you have been doing it earlier. Firefox suggests to save image in the webp format.

Here is a solution to avoid this issue and save the pictures in their original format (by the worth of increasing your Internet traffic).

1. open the page about:config
2. click the button I accept the risk
3. in the search bar type network.http.accept.default
4. double click on the found parameter
5. remove the substring image/webp
6. apply modification by pressing the button OK

That's so! After this you can continue surffing in your usual manner. All the pictures will be downloaded in their original format.

To revert to the original value do the right click on this parameter and apply the command Reset. So your Firefox accepts webp again.

Update:

After updating the Firefox instance on my computer I've found that the suggestion of this article doesn't work. In this case (FF 65.0.2) the following modification should be applied (I tested it earlier with FF 65.0.1 but it didn't work):

1. open the page about:config
2. click the button I accept the risk
3. in the search bar type image.http.accept
4. double click on the found parameter
5. remove the substring image/webp
6. apply modification by pressing the button OK

Another related pages

1. Firefox 65 supports Google's WebP Image format
2. How to avoid saving images in webp format in Google Chrome 
3. Related discussion on Russian Mozilla forum