SiYuan

SiYuan is a local-first, self-hosted knowledge workspace for people who want linked notes, research material and AI writing tools in one place. Its block references let you connect individual passages rather than whole documents, with bidirectional links to follow those connections. It's open source under AGPL-3.0.

The Markdown editor displays formatting as you write. You can work with outlines, zoom into a block, or keep documents side by side in split views. Notes can include mathematical formulas and diagrams, while web clipping and links to PDF annotations help connect writing to reference material.

Beyond documents, SiYuan has database tables and spaced repetition flashcards. Tesseract OCR handles text recognition. Export options include standard Markdown with assets, plus PDF, Word and HTML, so your work can leave the workspace in familiar formats.

AI writing and question-and-answer chat use the OpenAI API. Those requests go to an external service; the knowledge workspace itself can run on your own hardware or server. An API and a built-in command-line interface give AI agents and other tools access to workspace data. The CLI doesn't require a running server.

SiYuan runs on Windows and Linux, with apps for Android, iOS and HarmonyOS. It also offers end-to-end encrypted sync. Docker hosting provides browser access, but that deployment doesn't connect to the desktop or mobile apps and doesn't support Markdown file import or PDF, HTML and Word export.