Re-encode a JPEG at the quality you choose, with the encoder settings that normally sit behind a paywall or aren't offered at all.
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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 JPEG files
Progressive coding, optimised Huffman tables and explicit chroma subsampling control — 4:4:4 when the image is text or a screenshot, 4:2:0 when it's a photo.
Quality is a live slider: the preview re-encodes as you drag it, so you pick the point where the artefacts start rather than guessing at a number.
Metadata, GPS coordinates and colour profiles are dropped by re-encoding, which is both a size win and a privacy one.