(Re-post of Crowdicity post which had 40 votes)
Unfortunately, many programs are not compatible/interoperable with the WebP format. Users need a simple way to save images in traditional formats such as JPEG, PNG, and Animated GIF, which often is available from the server.
Since Firefox added image/webp to its Accept headers, server farms often add WebP compression to JPEG, PNG, and Animated GIF files, changing the internal file format without modifying the file extension. That is transparent to users, but there is an issue: when using Save Image As..., Firefox saves the WebP format.
Sites also are starting to use the <picture> tag with a WebP <source> that overrides the traditional format in the <img> tag.
Firefox users often want the original image format to facilitate editing in programs that don't accept WebP, or for other reasons. Whatever the reason, because Firefox doesn't make it convenient, they often resort to using Chrome instead.
Parity with Chrome
In Google Chrome, if the file name has its original .jpg or .png extension, the browser saves in the original format. This appears to be done through a re-request to the server, which is similar to the workaround employed by some Firefox users of opening the Page Info dialog, Media panel, and using the Save As button (this request does not include image/webp in the Accept headers).
I can tell this is a pain point based on Mozilla Support and r/Firefox posts, and because my WebP-related extensions have a surprisingly large number of users:
* "Save webP as PNG or JPEG (Converter)" -
14,757 users as of 6 March 2022 36,742 users as of Jan. 29, 2023 ( https://addons.mozilla.org/firefox/addon/save-webp-as-png-or-jpeg/ )
* "Don't "Accept" image/webp"-
7,092 users as of 6 March 2022 16,773 users as of Jan. 29, 2023 ( https://addons.mozilla.org/firefox/addon/dont-accept-webp/ )
So please, UX folks, take a look at this!