What it actually produces
Measured, not estimated. A procedurally generated 2400×1600 (3.8 MP) test image built to carry photographic entropy: value noise across nine octaves down to near-pixel scale, a dense field of small high-contrast features, a smooth gradient, hard edges and light grain. It is not a photograph — it is reproducible, which a photograph is not. Each figure below comes from running that image through this page.
| Input | Output | Change |
|---|
| 109 KB | 314 KB | 188% larger |
Your own files will differ — a photograph, a screenshot and a diagram compress very differently. The point of a fixed image is that the formats can be compared with each other, not that your result will match.
What is an AVIF file, and why do I have one?
AVIF is a still image wrapped in the AV1 video codec — a format designed by Google, Netflix, Amazon, Mozilla and others to cut streaming bandwidth, then adapted for still pictures.
It compresses dramatically better than JPG, which is why websites have started serving it. Save an image from a modern site and you may well get an AVIF, whether or not you wanted one.
Then you try to open it, and your photo viewer shrugs.
Why won’t my software open it?
Browser support for AVIF is now broad. Support everywhere else is not.
Most desktop photo viewers, a good deal of older editing software, most print workflows and plenty of upload forms still reject AVIF. The format is roughly where WebP was several years ago: fine on the web, awkward off it.
JPG has the opposite profile. It is thirty years old and universally supported, which is exactly what makes it the right destination here.
Expect a much larger file
On the fixed test image used for every measurement on this site, a 109 KB AVIF became a 314 KB JPG — close to three times larger.
Nothing malfunctioned. AVIF is simply a far more efficient format, and storing the same picture in an older one costs more space. You are spending bytes to buy compatibility.
If you need the file to stay small and the destination is a web page you control, WebP is a middle ground — 198 KB on the same test image, with much broader support than AVIF outside the browser.
Transparency will be lost
AVIF supports an alpha channel; JPG does not, and never has. Transparent areas become white.
Convert to PNG if that matters. Be ready for the size: on our test image the PNG came out around nineteen times larger than the AVIF.
Questions
- What is an AVIF file?
- AVIF is a modern image format built on the AV1 video codec, developed by a consortium including Google, Netflix, Amazon and Mozilla. It compresses far harder than JPG at the same visual quality, which is why websites increasingly serve it — and why you may have downloaded one without meaning to.
- Why won't my software open AVIF?
- Because support outside browsers is still thin. Every current browser renders AVIF, but many desktop photo viewers, older editors, print workflows and upload forms do not. Converting to JPG removes the problem.
- Why is the JPG so much bigger than the AVIF?
- Because AVIF compresses far better. On the fixed test image used here, a 109 KB AVIF became a 314 KB JPG — nearly three times larger. That is the price of a format everything can read, not a sign of a failed conversion.
- Does converting lose quality?
- A little. Both formats are lossy, so decoding and re-encoding discards a small amount more detail. At the default quality of 82 the difference is not visible at normal viewing sizes.
- What happens to transparency?
- It is lost. AVIF supports an alpha channel and JPG does not, so transparent areas are filled with white. Convert to PNG instead if you need to keep them.
- Is my image uploaded?
- No. Decoding and encoding both run inside this browser tab. The Uploaded readout beside the result measures the page's own outbound traffic, so a successful conversion reads 0 B.
- Is there a file size limit?
- None imposed. There is no upload and no server, so your device's memory is the only ceiling.
- Can I convert several files at once?
- Yes. Add as many as you like — there is no upload, so no queue and no per-file cap.
- Should I convert to JPG or PNG?
- JPG for photographs and anywhere file size matters. PNG when the image has transparency or contains text and sharp graphics — at the cost of a much larger file, around nineteen times larger on our test image.
- Will there be a watermark?
- No. Nothing is added to the image and there is no paid tier.