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HTMLProofer vs muffet: catalog facts
HTMLProofer	muffet
Free Free and open source.	Free Free and open source.
Windows, macOS, Linux, Command line	Windows, macOS, Linux, Command line
Checks generated output rather than source templates Works well in CI for static sites	Fast concurrent crawling Fits easily into CI pipelines
Requires a Ruby environment Works on local HTML files rather than crawling live sites	Command line only, no graphical interface Focused on links rather than wider SEO or markup checks
Downloadable app	Downloadable app
Open source	Open source
License not stated	License not stated
No account needed	No account needed
Not stated if it works offline	Not stated if it works offline
Official website Full listing and sources Checked September 23, 2026	Official website Full listing and sources Checked September 23, 2026

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