YES! Finally. Firefox Nightly users needed to enable the feature manually to get it supported in the Firefox browser at the time. Starting with version 86, which will be available on the 23th of February, 2021, Firefox is going to support AVIF by default.
Update December 2020
There has been other industry adoption for AVIF images, such as Microsoft with Windows. Google added support for AVIF to Chrome earlier this year and shipped it with Chrome 85. Mozilla Firefox is also very soon expected to enable support for AVIF as an image format based on AV1 video coding. Mozilla has announced that current AVIF image support is complete. Also, they claim previously encountered problems with the format have been resolved. There was a Mozilla bug ticket tracking the default support of AVIF. The patch enabling default support has initially been pushed but reverted as a result of broken tests. Those items have been reviewed and AVIF appears to be ready to land now. In any case, Firefox will support AVIF images with its next versions in early 2021. We can't wait for users to be able to directly use and view AVIF images. For those looking to convert their images to AVIF, try out our fastest converter. It works with Firefox already.
Starting in version 77 (released in June 2020), Mozilla recently implemented experimental support for the AVIF image format in Firefox. The feature is not enabled by default in the web browser's production version. Still, users interested in adding support may do so at the time of writing. When enabled, Firefox will render AVIF image files just like any other image format supported by the web browser. AVIF was developed from the AV1 video format and uses HEIF as the container and AV1 frames. It is a new format. AV1 is already supported in most web browsers, and the work has begun to integrate AVIF too.
Check your version
If you would like to find out your browser's version, open its settings and help menu and click 'about'. If you have version 77 or above, you will be able to use the tutorial below to enable the AVIF image format.
Enable AVIF support in Firefox
Provided that you have installed a compatible version, you can easily add support for AVIF with the about:config configurations. Type ‘about:config’ (without the asterisks) inside the address bar and press Enter. Most likely a warning message will appear, telling you to be careful. No worries, we will be handling everything gently. Click on 'Accept the risk and continue'. In the search bar at the top of the page, search for avif. The option ‘image.avif.enabled’ is the one you are looking for. If the second column's value is showing 'false', click the right switch button to set it to true. A 'true' value means that Firefox supports AVIF, whereas a 'false' value means the browser's image format isn't supported.
Mozilla considers support to be experimental. However, most AVIF files should be rendered successfully, and full native support is expected to arrive in the early months of 2021.
Remember to restart Firefox. Then come back to this page to see this fantastic image: