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OptiPNG vs FileOptimizer: catalog facts
OptiPNG	FileOptimizer
Free Free and open source under the zlib licence.	Free Free and open source under the AGPL-3.0 licence.
Windows, Command line	Windows
Lossless recompression of PNG files Converts BMP, GIF, PNM and TIFF to optimized PNG	Lossless size reduction with no quality loss Supports a very wide range of file formats
Command line only, no graphical interface Lossless only, so savings are smaller than lossy tools	Windows only Size savings depend heavily on the file type and how it was created
Downloadable app	Downloadable app
Open source	Open source
License: Zlib	License: AGPL-3.0-or-later
No account needed	No account needed
Works offline	Works offline
Official website Full listing and sources Checked October 2, 2026	Official website Full listing and sources Checked October 2, 2026

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