JPG vs PNG vs WebP vs AVIF: file sizes measured
For photographs, WebP gave the smallest files in our test, 20 to 41 percent under JPEG, while AVIF kept the most detail. PNG was 8 to 17 times the size of JPEG. For screenshots and graphics, WebP and AVIF came out about half the size of JPEG and closer to the original.
How big is each format?
We saved five photographs and two graphics in all four formats with this site's free online image converter, at its default quality of 82. Same pixels, same size, only the format changed.
| Image | JPEG | PNG | WebP | AVIF |
|---|---|---|---|---|
| Waterfall in forest (3072 x 2048) | 1,168 KB | 12,754 KB | 903 KB | 1,256 KB |
| Cityscape with signage (3904 x 2602) | 1,755 KB | 21,421 KB | 1,075 KB | 1,580 KB |
| Sunflower, blurred background (2434 x 1697) | 453 KB | 7,588 KB | 268 KB | 389 KB |
| Mountain range and sky (2971 x 1615) | 709 KB | 10,177 KB | 467 KB | 648 KB |
| Waterfall, close crop (1280 x 959) | 341 KB | 2,699 KB | 274 KB | 320 KB |
| Screenshot of a web page (1280 x 900) | 69 KB | 131 KB | 34 KB | 36 KB |
| Share card with text (1200 x 630) | 43 KB | 109 KB | 24 KB | 23 KB |
PNG keeps every pixel exactly, which is why a photograph comes out 8 to 17 times the size of a JPEG. WebP was the smallest on all five photographs.
AVIF was smaller than JPEG on four of the five photographs, not all. On the forest waterfall it came out about 8 percent larger.
Which one keeps the most detail?
Size alone is half the answer, because the same quality number means different things in each format. SSIM measures how close a picture stays to the original, where 1 means identical.
| Image | JPEG | WebP | AVIF |
|---|---|---|---|
| Waterfall in forest | 0.9778 | 0.9719 | 0.9870 |
| Cityscape with signage | 0.9848 | 0.9702 | 0.9887 |
| Sunflower, blurred background | 0.9646 | 0.9578 | 0.9687 |
| Mountain range and sky | 0.9775 | 0.9663 | 0.9805 |
| Waterfall, close crop | 0.9897 | 0.9792 | 0.9954 |
| Screenshot of a web page | 0.9936 | 0.9978 | 0.9969 |
| Share card with text | 0.9941 | 0.9983 | 0.9992 |
On every photograph, AVIF stayed closest to the original and WebP drifted furthest. So part of WebP's smaller file is detail it let go.
The differences are small: all fifteen lossy photo files scored above 0.95.
Why is quality 82 not the same in every format?
Each encoder decides for itself what a quality number means. At 82, WebP throws away more than JPEG does, and AVIF keeps more. Compare the file size and the picture, not the slider.
When should you use PNG?
When every pixel must survive: logos, diagrams, screenshots you will edit again, and anything with a transparent background that has to stay sharp. Of the four, as this site saves them, PNG is the only one that never changes a pixel.
On the screenshot and the share card, PNG was only about two to two and a half times the size of JPEG, because flat colour compresses well without loss. On a photograph it is the wrong choice.
Which format should you pick?
For photos on a website you control, WebP for the lightest page, or AVIF when detail matters more. For a form or an app that asks for JPG, JPG.
For a logo or a screenshot, PNG if it must be exact, WebP if it must be light.
The format matters less than the width, though. How to reduce image size for a website, measured shows resizing to 1600 pixels took 87 to 96 percent off four of the same photos.
Convert JPG to WebP and Convert JPG to AVIF do the switch in your browser, and show the file size before you download.
How was this measured?
Each image went through this site's converter in Chrome on 25 September 2026, at full size. SSIM compares brightness in 8 by 8 pixel windows against the PNG export, which is the browser's own lossless copy of the input.
The photographs are the same five Wikimedia Commons images behind this site's file size pages. The graphics are a screenshot of this site's documents page and one of its share cards.
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