SiYuan

SiYuan is a personal knowledge management system organized around content blocks. Instead of files referencing each other loosely, every block can be referenced, linked both ways, zoomed into and queried, so notes stay connected without a separate index to maintain.

The editor is Markdown WYSIWYG with list outlining and support for documents running to a million words. It renders mathematical formulas, charts, flowcharts, Gantt charts, timing diagrams and staves, and it handles web clipping and PDF annotation links.

The surrounding features go well past note taking.

• SQL queries: embed query results directly inside a document.
• Database views: organize content in a table view.
• Flashcards: spaced repetition is built into the app rather than bolted on.
• Export: standard Markdown with assets, PDF, Word and HTML, plus copy targets for WeChat MP, Zhihu and Yuque.
• Snippets: template, JavaScript and CSS snippets adjust behavior and appearance.
• AI: writing and question answering through the OpenAI API, with Tesseract OCR alongside.

Desktop and mobile apps cover Android, iOS and HarmonyOS, and a Docker image serves a workspace over port 6806 with a lock screen access code and configurable user and group ids for host mounted directories. An HTTP API and a community marketplace extend it further. Most features are free including commercial use, while some are reserved for paid members.