PNG is lossless, so the only ways to shrink one are to store the same pixels more cleverly or to store fewer distinct colours. This does both, in your browser.
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80
Resize
50
Encoder detail
6
fastzopfli
256
28
0 lossless51 tiny
The largest saving available.
50
Speed, audio and advanced
8
0 smallest13 fastest
128
96
Advanced
8
Nearly all of the saving comes from the images inside.
150
75
Advanced
50
aggressivegentle
Advanced
14
coarsefine
0 merges only exactly equal vertices. A small value also closes hairline cracks left by CAD exporters.
Geometry only — texture coordinates,
materials and vertex colours are not carried through. Decimating a
UV-mapped mesh correctly is a much harder problem, and mangling your
UVs quietly would be worse than leaving them alone.
12
6
Advanced
ZIP and 7z. 7z encrypts the file list too.
What actually shrinks PNG files
Adaptive per-row filtering, then zopfli instead of ordinary deflate — typically several percent past what most tools manage, and the file stays a completely standard PNG.
Palette reduction is the dramatic one: screenshots, logos and flat artwork carry far fewer real colours than 24-bit allows, and dropping to a 256-entry palette turns four bytes per pixel into one.
A photograph usually ends up smaller as WebP or JPEG than as any PNG. Auto mode tries all of them and keeps whichever actually wins.