Photos shrink, graphics may not
JPG is built for photos. The test photo stored as a PNG went from 3.75 MB to 446 KB, 88% smaller, at quality 88. The screenshot went the other way, from 46 KB to 69 KB, because PNG already stores flat colours and text very efficiently.
So convert photos and scans to JPG freely. For interface screenshots and logos, keep the PNG unless a form or app insists on JPG.
| Test image | PNG | JPG | Change | Fidelity (PSNR) | Time |
|---|---|---|---|---|---|
| Photo | 3.75 MB | 446 KB | 88% smaller | 35.0 dB | 654 ms |
| Screenshot | 46 KB | 69 KB | 51% larger | 42.8 dB | 265 ms |
| Illustration | 94 KB | 43 KB | 55% smaller | 44.8 dB | 172 ms |
Test images are synthetic files made by this project: a 2000 x 1333 landscape photo, a 1600 x 900 interface screenshot and a 1200 x 1200 transparent illustration. The illustration has transparent areas, which JPG cannot store, so they are filled with white. Flat interface graphics can come out larger as JPG than as an optimised PNG. 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.
Transparent areas become a colour
JPG cannot store transparency. Transparent and half-transparent pixels are blended onto the background colour, which is white unless you change it in Advanced settings. The test illustration shows this: its transparent corners became white and the file went from 94 KB to 43 KB.
If you need the transparency, convert to WebP instead, which keeps it.
Choosing the quality
Quality 88 is the default here because PNG files are often screenshots with text, and text shows JPG artefacts sooner than photos do. For photos, 80 is usually enough and saves more. For screenshots with small text, try 92. Use Compare at 100% to see the difference on your own file.
For forms and email
Upload forms that ask for a JPG often also have a size limit. If yours does, open Advanced settings and set a target size, or use one of the pages such as compress to 100 KB. The tool then picks the quality for you.
Several files and their names
Drop a whole folder of PNG files and each one becomes a JPG. Up to five start on their own; for more, press the button in the bar at the bottom. The new files keep their original names with a .jpg ending. To add the pixel size or a number to each name, open File names in Advanced settings. Download one at a time or all of them as a ZIP.
Metadata
PNG files can carry text chunks with software names, AI prompts and settings. These are removed with the rest of the metadata unless you keep it. The metadata viewer shows what a file contains before you share it.
Questions
Why did my PNG get bigger as a JPG?
It was probably a screenshot or a graphic with flat colours. PNG handles those very well; JPG suits photos.
What happens to a transparent background?
It is filled with the background colour, white by default. You can pick another colour in Advanced settings.
Is the conversion private?
Yes. It runs in your browser and the image is not uploaded.