Will the JPG be bigger or smaller than the AVIF? With AVIF it can go either way. Sites use AVIF because it squeezes photos hard, and how hard decides what happens when you turn one into a JPG.
Two files, two directions
| Image | AVIF | JPG | Change |
|---|---|---|---|
| Cat photo, 451×300 | 21.1 KB | 27.0 KB | +28% |
| Hubble Deep Field, 1000×872 | 165 KB | 162 KB | −2% |
Both AVIFs were saved at the same quality setting, and the JPGs were written at quality 85. The small cat photo grew, because AVIF had packed it more tightly than a quality-85 JPEG does. The large Hubble picture, mostly black sky dotted with small galaxies, came out a little smaller. So don’t pick this conversion to save space, and don’t fear it either: expect a size in the same range, and check the numbers the tool shows next to each file.
Each file took well under a second. The very first one also loads the AVIF decoder, so it is the slowest.
Why you would convert at all
AVIF files mostly reach you by saving an image from a website that serves them. Current browsers show them, but plenty of desktop apps, older phones, print services and upload forms still do not accept them. JPG is the safe answer for all of those.
Colors and HDR
If the AVIF has a color profile, the JPG keeps it, so colors match what the browser showed. HDR is different: a JPG cannot store it. If the tool spots an HDR or very wide color space AVIF, a note appears under the result: “This image is HDR or uses a color space that a JPG or PNG cannot hold, so colors may look flatter than in the original.”
When PNG is better
If the AVIF has a transparent background, a JPG fills it with white. If you plan to keep editing the picture, every JPG save adds a little loss. In both cases use AVIF to PNG, at the cost of a much bigger file.