What it is

SiYuan is an open-source, self-hosted knowledge management system built for privacy-first workflows. It operates as a local-first workspace where users store data in encrypted repositories on their own infrastructure, avoiding reliance on third-party cloud services. The project lives in the productivity and utilities ecosystem, specifically targeting note-taking and knowledge management use cases, and positions itself as a privacy-respecting alternative to Notion.

It solves the problem of fragmented, vendor-locked knowledge work by enabling block-level linking, two-way references, and local-first editing without sacrificing collaborative or AI-assisted capabilities. Users retain full control over their data while gaining tools for structured writing, querying, and integration with AI agents via MCP and OpenAI-compatible APIs.

Key capabilities

• Block-level referencing and two-way linking for granular knowledge connections
• Markdown WYSIWYG editor with support for mathematical formulas, charts, flowcharts, Gantt charts, timing charts, and musical staves
• SQL query embedding for dynamic data extraction and display within notes
• Local-first data storage using encrypted data repos (dejavu) with optional sync via third-party services
• AI writing assistance and Q&A chat via configurable OpenAI API endpoints
• Export to PDF, Word, HTML, and platform-specific formats (WeChat MP, Zhihu, Yuque)
• Plugin system (petal) and REST API for extensibility and automation

Who uses it and how

• Individuals self-hosting SiYuan on personal servers or NAS devices for secure, offline-capable knowledge bases
• Teams using Docker or Unraid deployments to collaborate on shared documentation while keeping data on-premises
• Researchers and writers leveraging block-level linking and SQL embedding to build interconnected, queryable research notes

Getting started

SiYuan offers Docker images (b3log/siyuan), native installers via its homepage, and package managers (e.g., snap, homebrew). The README outlines CLI usage (siyuan server), Docker deployment (-v volume mounts for data persistence), and hosted options via community marketplaces.

When to use it — and when not to

SiYuan replaces Notion for users prioritizing data sovereignty and local-first operation, but requires managing its own SQLite-based data repo, encryption keys, and optional SMTP for notifications. It lacks built-in real-time collaboration or role-based access control—features present in paid alternatives—so teams needing those must supplement with external tooling or accept limitations. The AGPL-3.0 license mandates source disclosure for modified deployments, which may deter some commercial users.