Compress PNG

Compress PNG: what lossless and 256 colors each saved

We ran four PNGs through this tool on 10 November 2026; the table above lists the results for those four PNGs. Lossless, which repacks the data without changing a pixel, made them 6% to 35% smaller: 20% on the 1536 × 1024 transparent product cutout, 15% on the 3200 × 2400 screenshot, 6% on the 1448 × 1086 photo stored as PNG and 35% on the 2068 × 480 logo. 256 colors made the same files 67% to 75% smaller; all four together went from 5.92 MB to 1.71 MB.

In Compare with original, zoomed to 150–225%, the 256-colour logo and screenshot looked the same as their originals; the logo's colours moved by at most 4 of 255 levels, on 7% of its pixels. The photo showed no banding in its soft background. The sneaker cutout showed the one visible change: small grey flecks on the white upper turned brownish.

The gap between Lossless (6–35% smaller) and 256 colors (67–75% smaller) is why this page starts at 256 colors. Lossless is the better pick for a source file you will edit again, or when exact colours matter, such as brand colours or a mockup with long smooth gradients. Your own PNGs will land at different sizes depending on how many colours they contain.

Test conditions: this tool in Chrome on a Mac, Compress by quality, Output format left on Original format for Lossless and 256 colors. Sizes come from each file's byte count, with 1 KB = 1000 bytes and 1 MB = 1000 KB, rounded to the last digit shown. The tool itself rounds sizes up, so its summary line for the 256-colour batch read 1.72 MB.

Why the transparency survives fewer colours

A reduced PNG keeps its colours in a palette of at most 256 entries, and the format allows each entry its own opacity. The W3C Portable Network Graphics (PNG) Specification (Third Edition) describes the tRNS chunk as holding "alpha values that are associated with palette entries (for indexed-color images)", and limits a palette to 256 entries, which is where the 256 in Reduce colors comes from.

All four results in our test were saved as indexed-colour PNGs. Every pixel of the logo kept exactly the same opacity as before. The sneaker cutout, whose edges and shadow are almost entirely semi-transparent, kept its transparent background too, though not pixel for pixel: 1,541 of its 1,009,008 semi-transparent pixels became fully transparent, and 905,819 pixels shifted in opacity, by 3.5 of 255 levels on average.

A photo saved as PNG: compress it or change the format?

Of our four PNGs, the photo was the hardest to shrink. Lossless took only 6% off our 1.95 MB photo, and while 256 colors made it 67% smaller, photos usually contain many more shades than flat graphics, so reducing them is more likely to show on a photo; check yours in Compare with original. Changing Output format went much further: JPG at quality 75 gave 106.6 KB and WebP at quality 75 gave 68.0 KB.

JPG cannot store transparency; the tool paints those areas white. For the logo, JPG was even the bigger file (30.6 KB against 19.5 KB as a 256-colour PNG). WebP kept every transparent pixel in our test and made the logo 15.3 KB, but check that the site you upload to accepts WebP. If all you want is a plain format switch, use PNG to JPG.