An AVIF file is an image saved with the AV1 codec — the same compression used for video — which makes it roughly 30–50% smaller than a JPG of the same quality. Every current browser displays it, which is why you keep downloading them. The trouble starts everywhere else: plenty of desktop applications, email clients and upload forms still refuse it. You can convert AVIF to JPG in your browser without uploading the file.
Why you keep ending up with AVIF files
AVIF adoption happened on the web first and almost invisibly. Sites serve it because it cuts bandwidth substantially at the same visual quality, and your browser accepts it without comment — so you never notice until you right-click and save. Then you have a file with an extension you have never seen, and the image that displayed perfectly a moment ago won't open.
Nothing has gone wrong. The picture is fine. The gap is that browser support and application support are two different things, and they moved at very different speeds.
What actually rejects AVIF
Support is close to universal in browsers and patchy everywhere else. The failures people hit most often are these:
- Upload forms that whitelist extensions — job portals, government sites, print services and most CMS media libraries were written before AVIF existed and simply reject the file
- Email and chat clients, where the attachment arrives as a generic icon with no preview
- Older desktop image editors, which need a plugin or a newer release
- Photo printing services, which almost universally expect JPG
That list is the whole reason AVIF conversion is a common task rather than a niche one. The format is not the problem; it is that the file has to travel somewhere that has not caught up.
AVIF compared with the formats you already know
Against JPG, AVIF is dramatically more efficient and adds capabilities JPG never had — transparency, high dynamic range, wide colour gamut. Against WebP, it compresses better still, particularly at low bitrates where WebP starts to smear detail. Against PNG, it is far smaller, but PNG is lossless and AVIF (as normally encoded) is not, so PNG remains the right answer for screenshots, diagrams and anything with crisp edges you cannot afford to soften.
The practical summary: AVIF is the better format on nearly every technical measure, and JPG is still the format that works everywhere. Which matters more depends entirely on where the file is going next.
Converting AVIF without uploading it
Because your browser already contains an AVIF decoder — that is how it displayed the image in the first place — converting one needs no server at all. File Converts decodes the AVIF locally and re-encodes it on your own machine, so the file never leaves your device. Choose AVIF to JPG for photographs and anywhere a smaller file matters, or AVIF to PNG when the image has transparency you need to keep.
One thing to expect: the JPG or PNG you get back will usually be larger than the AVIF it came from, sometimes by several times. That is not a fault in the conversion — it is the compression advantage you are giving up in exchange for a file everything can open.
Should you keep the original?
If it is an image you may edit or re-export later, yes. Converting AVIF to JPG is lossy in both directions: the AVIF was already lossily encoded, and re-encoding as JPG loses a little more. For one pass at sensible quality that is invisible, but repeatedly converting the same image back and forth will slowly degrade it. Keep the AVIF as the master and treat the JPG as the copy you send.