BraiNOTES Brings Handwritten Notes to Lecture PDFs in a Browser Tab

The tool is aimed at students who take notes on convertible laptops. The developer wrote that existing apps had made it difficult to take notes from one device to another, export as PDF, or use without an account for many of them. BraiNOTES is the version of the tool the developer wanted: open a tab, place lecture slides or multiple PDFs next to the page or make them the page, write on them with a pen, and leave data in the browser.

BraiNOTES uses perfect-freehand outlines for strokes and supports pen pressure. PDF files are rendered by pdf.js in a worker. For storage, it uses IndexedDB a moment after every change. The post says there is no account, no analytics, and the tool works completely offline and local-first.

Notebooks can be exported as .brainotes files, which the developer said are zip archives containing one JSON file per page plus the imported PDFs and pictures. The export keeps the original pages and places vectorized ink on top, so text in the slides remains selectable.

The tool has two main modes. In Study mode, the PDF opens on the side of the tab so a user can read it while taking notes, and a snip tool can capture a formula or diagram directly into the notes for writing around it. In Board mode, users get a whiteboard for tutoring or additional exercise space, and can highlight or draw with a laser pointer tool while presenting.

The developer described the ink as appearing the moment the pen moves, with a one euro filter to calm shaky hands while writing and a light refit when the pen is lifted. The project can be tried at notes.swimmingbrain.dev, and its repository is on GitHub under an MIT license.

The post follows TeXbrain, a LaTeX editor that runs completely in the browser with no account or server. The developer wrote in August that TeXbrain received more feedback, bug reports, and help than expected, and said BraiNOTES applies the same approach to the other half of their studies, handwritten notes.

The developer said BraiNOTES has been used for every lecture in the last few months, and that a few friends use it too. Bug reports, fixes, recommendations, and feedback are welcome, according to the post.

The same GitHub profile also lists a video editor and an animation tool, both described as work in progress. The developer is working on an MCP server for each tool, which could let an MCP client do further things with notes or automatically edit videos. That feature will be off unless turned on and will only be able to talk to localhost, the post said.

At the time of the Hacker News listing, the post had 6 points and no comments. The listing included a comments URL at news.ycombinator.com/item?id=50049132.

Editor's Summary

BraiNOTES is a browser-based, local-first tool for taking handwritten notes on lecture PDFs, with no account, backend, or analytics. It supports Study and Board modes, exports notebooks as .brainotes files, and stores data in IndexedDB. The developer says it has been used for recent lectures and plans MCP server support for its tools.