About Hypothesis
Hypothesis is the right tool for annotating, not for saving a reading list. It is widely used in classrooms and research. Check the sharing setting before you highlight anything private, because annotations are public by default.
You can highlight and comment on web pages, PDFs and EPUBs. Each note attaches to the exact passage, and you can add tags and replies, so a class or team can annotate the same article together. University library guides say you can choose Only Me or a private group instead of public, and that free accounts can create private groups.
It is made by Annotation Unlimited, PBC, and the browser extension is open source under a BSD licence. The Chrome listing says it handles personally identifiable information. Browser coverage is thin: the README still marks Firefox as in development, and we found only unofficial tools on Firefox Add-ons, so treat it as a Chrome extension. It does not keep a reading queue either, so pair it with a reader or clipper. Choose it if annotation is the job.
Pros and cons
- Annotates web pages and PDFs, with tags and private groups
- Open source browser extension under a BSD licence
- Updated October 2026
- Free for personal annotation according to university guides
- Annotations default to public unless you pick a private group or Only Me
- Chrome Web Store only: no finished Firefox extension is listed
- Not a read-later queue, and a 3.9 star Chrome rating
Permissions
The Chrome listing says it handles personally identifiable information. We did not read its manifest, but an annotation tool needs to read and modify the pages you annotate.
