Hypothesis: Annotate with anyone, anywhere


An open community project.

  • We’re a mission-driven nonprofit.
    Dedicated to enabling layers of conversation over the world’s knowledge.

  • Building an open platform
    That works everywhere, based on open-source technology and interoperable standards.

  • As a part of a global community.
    Working with others across the world to advance human understanding for the public good.

Learn More about Hypothesis.


The Hypothesis Project is a new effort to implement an old idea: A conversation layer over the entire web that works everywhere, without needing implementation by any underlying site.

Our team creates open source software, pushes for standards, and fosters community.

Using annotation, we enable sentence-level note taking or critique on top of news, blogs, scientific articles, books, terms of service, ballot initiatives, legislation and more. Everything we build is guided by our principles. In particular that it be free, open, non-profit, neutral and lasting to name a few.

We are a non-profit organization, funded through the generosity of sponsors like the Knight, Mellon, Shuttleworth, Sloan, Helmsley, and Omidyar Foundations—and through the support of thousands of individuals like yourself that want to see this idea come to fruition. You can donate to our effort, or view our tax returns.


Hypothesis server

h is the web app that serves most of the https://hypothes.is/ website, including the web annotations API at https://hypothes.is/api/. The Hypothesis client is a browser-based annotator that is a client for h’s API.

GitHub - hypothesis/h: Annotate with anyone, anywhere.

Hypothesis client

The Hypothesis client is a browser-based tool for making annotations on web pages. It’s a client for the Hypothesis web annotation service. It’s used by the Hypothesis browser extension, and can also be embedded directly into web pages.

GitHub - hypothesis/client: The Hypothesis web-based annotation client.

Hypothesis documentation