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Curtail vs OptiPNG: catalog facts
Curtail	OptiPNG
Free Free and open source under the GPL-3.0-or-later.	Free Free and open source under the zlib licence.
Linux	Windows, Command line
Handles PNG, JPEG, WebP and SVG Uses proven tools like oxipng and pngquant	Lossless recompression of PNG files Converts BMP, GIF, PNM and TIFF to optimized PNG
Linux only Compression only, no other editing	Command line only, no graphical interface Lossless only, so savings are smaller than lossy tools
Downloadable app	Downloadable app
Open source	Open source
License: GPL-3.0-or-later	License: Zlib
No account needed	No account needed
Works offline	Works offline
Official website Full listing and sources Checked October 1, 2026	Official website Full listing and sources Checked October 2, 2026

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