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Klia Kompress vs Caesium Image Compressor: catalog facts
Klia Kompress	Caesium Image Compressor
Free No price is mentioned; the app is published on Flathub under a proprietary EULA.	Free Free and open source under the GPL.
Linux	Windows, macOS, Web
Processes files locally without uploading Batch conversion with quality control	Batch processing with visible before and after sizes for the whole folder Resize at the same time as compressing, in one pass
Proprietary, source not published Very new project with little history	No official Linux binary; you compile it or use a third-party build Windows 10 build 1809 or later and macOS 12 or later, 64-bit only
Downloadable app	Downloadable app, Web application
Closed source	Open source
License: Proprietary EULA	License: GPL-3.0
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 September 21, 2026

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