What AVIF is and why it causes trouble
AVIF is an image format based on the AV1 video codec, released in 2019 by the Alliance for Open Media, a group that includes Google, Apple, Microsoft, Netflix and Mozilla. It squeezes photos into remarkably small files and supports transparency, HDR and animation, which is why more and more websites serve it.
Software outside the browser has been slower to catch up, so an AVIF saved from a site may not open in an older photo viewer, office suite or upload form. Choose JPG for the widest support, PNG for lossless editing with transparency, or WebP for a light web image that keeps transparency.
Browser support
Decoding uses the AVIF support built into your browser, so nothing is uploaded and no extra software is downloaded. Current versions of Chrome, Edge, Firefox and Safari all read AVIF; Safari needs macOS Ventura or iOS 16 or later. If your browser is too old, the converter tells you so instead of failing silently.
What to expect
Animated AVIF files are converted from their first frame, and HDR pictures are mapped to standard range. Converting to AVIF is not offered yet, because browsers can read the format but cannot write it.