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OptiPNG vs pngcrush: catalog facts
OptiPNG	pngcrush
Free Free and open source under the zlib licence.	Free Free to use, modify, and redistribute under the license described with its source.
Windows, Command line	Windows, Linux, Command line
Lossless recompression of PNG files Converts BMP, GIF, PNM and TIFF to optimized PNG	Tries compression levels and PNG filters to reduce file size Can remove or add ancillary PNG chunks
Command line only, no graphical interface Lossless only, so savings are smaller than lossy tools	It is a command-line application.
Downloadable app	Downloadable app
Open source	Open source
License: Zlib	License: libpng license equivalent
No account needed	Not stated if an account is needed
Works offline	Not stated if it works offline
Official website Full listing and sources Checked October 2, 2026	Official website Full listing and sources Checked October 8, 2026

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