Free tool
Read a paper one passage at a time
Open a research paper as a PDF and read it as published. Highlight any paragraph to get its key points, a plain explanation, or an answer to your question in the margin, and leave your own comments as you go.
Guide
How it works
- Drop in a PDF. It opens exactly as published, figures and equations included.
- Select a passage and choose Key points, Explain, or Ask. The answer appears beside that passage.
- Choose Comment to write your own note. Notes stay lined up with the text they belong to.
- Export your notes as Markdown, or download the PDF with your highlights and notes built in.
Guide
Built for reviewing and studying papers
Summaries work on the passage you pick, not the whole paper, so you can check each claim against the text right next to it. Answers come only from the paper. When the passage does not answer your question, the reader says so instead of guessing.
FAQ
Before you start.
Is my paper uploaded?
No. The PDF stays in your browser. Only the passage you highlight, the text around it, and the start of the first page (the title and abstract) are sent to the AI, and only when you ask for a summary, an explanation, or an answer.
Are my notes saved?
Yes, in this browser. Open the same PDF again on this device and your highlights and notes come back. Export them to keep a copy anywhere else.
Is it free?
Yes. Without an account you get 5 AI summaries a day. With a free account you get up to 100 a day. Comments and exports are always unlimited.
Does it work with scanned PDFs?
Not yet. A scanned paper has no selectable text, so there is nothing to highlight. Papers from journals and arXiv almost always have text.
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