What changes when a JPG becomes PNG
PNG stores every pixel exactly, while JPG throws some detail away to stay small. So the PNG copy is always larger. The 2000 x 1333 test photo grew from 694 KB to 3.08 MB. The screenshot that had been saved as a JPG grew less, from 86 KB to 145 KB, because flat colours pack well in PNG.
The picture itself looks the same as the JPG. Converting cannot bring back detail the JPG already dropped, and any blocky edges stay.
| Test image | JPG | PNG | Change | Pixels | Time |
|---|---|---|---|---|---|
| Photo | 694 KB | 3.08 MB | 344% larger | 2000 x 1333 | 3.0 s |
| Screenshot saved as JPG | 86 KB | 145 KB | 70% larger | 1600 x 900 | 915 ms |
PNG stores every decoded pixel exactly, so a photo grows several times over. The screenshot JPG was saved from the test screenshot at quality 90. Converting cannot bring back detail the JPG already dropped. 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 PNG is worth it
- You will edit the image several times. Each save as PNG adds no new loss, unlike saving a JPG again.
- A website, an app or a print service only accepts PNG.
- You plan to cut out a background later in an editor and need a format that can hold transparency.
For anything that goes straight onto a web page or into an email, the JPG or a WebP copy is the better choice because it is much smaller.
Transparency
A JPG has no transparent areas, so the PNG has none either. The format can hold transparency, but a converter cannot know which parts should be see-through. Removing a background needs an editor.
Large photos
A photo straight from a phone has far more pixels than a screen shows, and as a PNG it becomes a very large file. If the PNG is for a document or a web page, set a longest side in Advanced settings, for example 1600 or 2000 pixels. The PNG is then a fraction of the size and still sharp. Files whose name says .jpg but which are really WebP or AVIF are read by their contents, so they convert too.
Size and speed
The PNG is packed with an optimiser after encoding, which keeps it as small as a lossless file can be. That takes a moment for large photos; the table shows the times on a single thread. In the browser several images run at once on different workers.
What else happens
Camera details and GPS location are removed by default. A photo saved sideways with a rotation tag is turned upright before conversion, so the PNG opens the right way round everywhere.
Questions
Does JPG to PNG improve quality?
No. The PNG keeps the JPG exactly as it is. It stops further loss, but it cannot undo loss that already happened.
Why is the PNG so much bigger?
PNG is lossless. Photos have fine detail everywhere, which lossless compression cannot shrink much.
Can I convert many JPGs at once?
Yes. Drop them together and download a ZIP.