Don't "Accept" image/webp

Firefox usually sends websites an indicator that it can handle WebP-format and AVIF-format images, and this may encourage sites to send images in those formats. This extension strips out one or both indicators from requests (more specifically, the Accept header) so sites are more likely to send JPEG and PNG format images.

Due to reported problems, Version 0.8 adds the option to exempt a site, and Patreon is exempted by default.

Version 0.9 automatically exempts Reddit images if you're running the "Load Reddit Images Directly" extension to resolve a conflict between the two. Please let me know if you discover any other extension conflicts.

Notes:

(1) Although broad permission is needed for this extension to modify the Accept header, no data is read from requests, responses, or web pages.

(2) This extension monitors and edits request headers using the onBeforeSendHeaders API. There is a possibility of a conflict with other extensions that use the same API, which can lead to inconsistent results for both extensions.

(3) Version 0.9 now checks whether to have conflicting extensions involved (currently only "Load Reddit Images Directly").

Note: since Firefox 68, users cannot directly edit the network.http.accept.default preference, so if you found an old solution of removing image/webp from that preference, you've found the right new workaround.