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pdfsizeopt vs 4K Image Compressor: catalog facts
pdfsizeopt	4K Image Compressor
Free Free and open source.	Freemium Free download with a paid premium upgrade.
Windows, Linux, Command line	Windows, macOS
Lossless size reduction Docker image available	Compress to a percentage or an exact target file size Batch processing of many images
Command-line only Updates are infrequent	Some features are reserved for the paid premium tier Closed source
Downloadable app	Downloadable app
Open source	Closed source
License: GPL-2.0	License not stated
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 2, 2026

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