JPG to PNG converter

What converting to PNG does

The converter decodes your JPG and stores the result as PNG, a lossless format: every pixel of the PNG is exactly the pixel the JPG showed. We checked this on a 2048 pixel photo saved as JPG at quality 85: not one of its 12.7 million stored values differed after conversion. The PNG was 1.28 MB, against 238 KB for the JPG, about five and a half times larger.

What PNG cannot do is bring back detail. A JPG has already thrown some away, and the PNG keeps the result exactly, blocks and smudges included. It also cannot make the background transparent by itself: the white behind a product photo stays white. Remove it with the background remover, which saves a transparent PNG.

Good reasons to convert

• You will edit the picture in several steps. Each time an edited JPG is saved, it loses a little more. A PNG can be saved as often as you like without any loss.
• A website, app or print service asks for PNG. The conversion meets the requirement without changing how the picture looks.
• You need a format that can hold transparency for later work in an editor. PNG supports it; JPG does not.

For sending or posting a photo, keep the JPG. It is already as good as it will get, and much smaller.

Does saving a JPG again damage it?

Less than people think, unless you change something between saves. We saved the same photo as JPG at quality 85 ten times in a row. After the first save it scored 0.9817 in SSIM, a measure of how alike two pictures look where 1 is identical; after ten saves, 0.9814, almost no change. Then we repeated it, trimming one pixel from the edges before each save, as a small crop or edit would. The score fell with every round, to 0.9607 after ten.

So convert to PNG before a series of edits, and export a JPG once at the end.

The colours setting

Full colour, the default, keeps the conversion lossless. Fewer colours shrink logos, icons and screenshots that were saved as JPG by mistake, since they only use a handful of colours. On photos it backfires: our photo at 256 colours came out at 1.42 MB, larger than the full colour PNG, and looked grainy, scoring 0.896. The fine dots used to fake missing colours are harder to compress than the photo itself.

If the PNG is too big

• Expect it to be several times the JPG. That is the price of lossless storage, not a fault.
• Cap the longest side at 1920 or 1280 pixels if the picture is for a screen. Half the width means a quarter of the pixels.
• Consider lossless WebP with PNG to WebP: it keeps every pixel too, in a smaller file, and every current browser opens it.

How we tested. A CC0 photo of coffee in knitted gloves, scaled to 2048 by 1556 pixels, saved as JPG at quality 85 with the MozJPEG encoder of this site and converted with the converter's own code in Chrome. Pixels were compared value by value; SSIM was computed on luma with an 11 pixel Gaussian window.