Why the JPG is bigger
AVIF is one of the most efficient image formats in use, and JPG is one of the oldest. The same picture takes more space as a JPG. In the test, an AVIF photo of 142 KB became a 326 KB JPG at quality 88, and the screenshot went from 12 KB to 66 KB.
That extra size is the price of a file that opens everywhere. The JPG does not gain any detail; it keeps what the AVIF had.
| Test image | AVIF | JPG | Change | Time |
|---|---|---|---|---|
| Photo | 142 KB | 326 KB | 129% larger | 803 ms |
| Screenshot | 12 KB | 66 KB | 452% larger | 234 ms |
| Illustration | 9.2 KB | 42 KB | 354% larger | 288 ms |
The AVIF inputs were made from the test images at quality 55. AVIF is much more efficient than JPG, so the JPG is always larger; that is the price of a file every app can open. Transparent areas become white. Timings: one thread of WebAssembly on Node v22.23.4, Intel(R) Xeon(R) Processor @ 2.10GHz, 2 cores, measured 2026-10-31. Other devices will differ.
When you need a JPG
- An upload form or a portal only accepts JPG or PNG.
- An older photo editor, viewer or printer app will not open AVIF.
- You want to send a picture to someone without worrying about their software.
Keeping the JPG small
If the JPG is too big for where it is going, lower the quality to about 80 for photos, or open Advanced settings and set a target size. The tool then lowers the quality until the file fits, and shrinks the pixels only if it has to. There are ready-made pages for common limits such as 100 KB.
Transparency and colour
AVIF can be transparent and JPG cannot, so transparent areas are filled with the background colour, white by default. Colours are converted to the standard web colour space, which is what most JPG viewers expect.
Files named .jpg that are really AVIF
Images saved from websites sometimes keep a .jpg or .png name while the data inside is AVIF or WebP, because the site served a modern format. An upload form then rejects the file even though the name looks right. This tool reads the format from the file contents, so it spots the real type and gives you a proper JPG. The result card shows the format it found, next to the pixel size.
Going the other way
To make AVIF files from JPG or PNG, use image to AVIF. For iPhone photos, see HEIC to JPG.
Questions
Does converting AVIF to JPG lose quality?
A little, because JPG is lossy too. At quality 88 the difference is hard to see.
Can I convert several AVIF files at once?
Yes. Drop them together and download them as a ZIP.
Do I need to install anything?
No. Decoding and encoding run in your browser.