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Image Optimizer vs pngquant: catalog facts
Image Optimizer	pngquant
Free Free and open source under the MIT licence.	Free Free and open source; the CLI is under GPL-3.0-or-later with some parts under HPND and…
Linux	Windows, macOS, Linux, Command line
Lossless compression with identical pixels Processes a whole folder at once	Large file size reductions with preserved transparency Adaptive dithering with less noise
Only PNG and JPEG Overwrites the original files in place	Command line only; graphical use needs a separate front end Lossy, so not suited to images that must stay pixel-exact
Downloadable app	Downloadable app
Open source	Open source
License: MIT	License: GPL-3.0-or-later
No account needed	No account needed
Not stated if it works offline	Works offline
Official website Full listing and sources Checked October 1, 2026	Official website Full listing and sources Checked October 1, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.