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Hypothesis vs Diigo: catalog facts
Hypothesis	Diigo
Free Free for individuals. Institutional and LMS integrations are paid.	Freemium Free to use, with premium features such as archived web pages.
Web, Browser extension	Web, Browser extension
Annotations anchor to the text and survive page reflow Private, group and public annotation layers on the same document	Highlights and sticky notes on web pages and PDFs Tags and a personal library for saved pages
Requires an account and stores annotations on their service Anchoring can fail if a page changes substantially	Page archiving requires a premium plan Closed source hosted service
Browser extension	Web application, Browser extension
Open source	Closed source
License: BSD-2-Clause	License not stated
Account needed	Not stated if an account is needed
Not stated if it works offline	Not stated if it works offline
Official website Full listing and sources Checked September 22, 2026	Official website Full listing and sources Checked September 24, 2026

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