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Free Ruler vs KRuler: catalog facts
Free Ruler	KRuler
Free Free and open source, with optional donations.	Free Free and open source under the GPL-2.0 or later.
macOS	Linux
Measures in pixels, millimeters or inches Single-key shortcuts for every main action	Measures on-screen elements directly Small single-purpose utility
macOS only Requires macOS Sonoma or later; older builds are on the releases page	Linux only Basic tool with a narrow purpose
Downloadable app	Downloadable app
Open source	Open source
License not stated	License: GPL-2.0-or-later
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 1, 2026

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