A second brain should belong to you.

During the time we spent making SecBrain, we noticed something odd about the category we were building in. We were calling these tools second brains, and yet almost none of them were ours. Our notes lived on someone else’s server. The very act of remembering, the most personal thing software can help you do, was happening behind a vendor’s terms of service. And we were being asked to be grateful for it, because the alternative was to manage our own infrastructure, write Markdown by hand, and hope our editor of choice was still alive in five years.

We thought you should be able to have both: the convenience of a finished, modern product, and the dignity of owning the thing you’d spent years building. So we set out to build that.

We built SecBrain around three commitments.

The first is that your data is yours to take with you. The web, desktop and iOS apps each keep a fast cached copy of your memos, so your editor and your search run where you are, even offline. The cloud copy keeps your devices in sync and stores your attachments. It is boring, useful, and easy to leave. We built the offline queue, the crash-safe persistence, and the bounded retry logic before we built anything else. Capture saves to your device first, online or not, and Markdown export is on every plan. That is a promise we hold ourselves to.

The second commitment is that the AI serves your notes, not the other way round. SecBrain uses a cloud model through our server, on our own accounts with Anthropic, OpenAI and Google, because most people want AI that works on the first day: nothing to install, no keys to manage, and an allowance set by your plan. When you ask your library a question, the answer cites the notes it drew on, so you can check it rather than take it on faith. We’d rather tell you exactly where your prompts go than pretend they go nowhere.

The third commitment is that we won’t build the parts we’d be ashamed to maintain. SecBrain is single-user by design. There are no team workspaces. There is no shared editing. There are no permissions to manage. We made this choice early and we’re holding it because every collaborative feature we’ve watched our peers ship has come at the cost of the four things we care most about: privacy, performance, simplicity, and the user’s sense of authorship. If you want a tool to think with someone else, the world has good ones. SecBrain is a tool to think with yourself.

We have a name for the way we think about this. We call it sovereignty. We don’t think there’s a better word for it in English. Privacy is about what other people can see. Sovereignty is about who decides. The difference matters more in software for thinking than it does almost anywhere else, because the alternative, a private place that someone else owns, is a contradiction in terms.

When we were drafting the project internally, we called it Sovereign Second Brain. We shortened the name to SecBrain because the product matters more than the manifesto. But the original name still tells you exactly what we believed when we started, and what we still believe now.

SecBrain is built on Tauri v2 and Rust on the desktop, on React and IndexedDB in the browser, on Swift 6 and SwiftUI on iOS, on a Chrome extension on Manifest V3. Sync writes to Postgres, and a WebSocket tells your other devices when to pull. The vectors and the full-text index live on your device: in IndexedDB on web and desktop, in SQLite with FTS5 on iOS. The graph renderer is Sigma.js. The editor is Tiptap. The spaced-repetition algorithm is SM-2, the same one Anki has used for two decades. We list these here because being open about the stack is part of the deal. You should know what your second brain is made of.

The product runs today on the web, macOS and Windows. The Chrome extension is built, and native iOS is submitted to the App Store, not promised. Weekly insights, the knowledge graph with its nine link types, and the daily review all work today.

And it’s free to try: the Free plan needs no card.

If you decide to make SecBrain part of how you think, we want you to keep doing it for years. Long enough that you’d be furious if we made any of the choices on this page differently. Long enough that you’d notice if anything changed. We’d like to be worth that.

The SecBrain team