SiYuan

SiYuan is a privacy-first personal knowledge management system built around the idea that your notes should live on your own hardware, not a company’s servers. It runs locally on your machine or in Docker on your own server, and everything stays offline unless you explicitly configure sync.

The editor is block-based and supports bidirectional links, database views, spaced repetition flashcards, and embedded math formulas alongside standard Markdown formatting. Backlinks, forward links, and a graph view let you visualize how ideas connect across your notes, making it useful for both day-to-day note-taking and longer-form knowledge building.

Database blocks bring spreadsheet-like functionality into notes: you can create tables with relations, rollups, and calculated fields tied to other blocks in your vault. This makes SiYuan a practical alternative to Notion for users who want data views without the cloud dependency.

The core application is free and AGPL-licensed. Sync between devices requires either self-hosting a SiYuan server via Docker or paying for the cloud sync tier. The self-hosted sync option gives you full data sovereignty with no third-party access to your notes.

With 44,000+ GitHub stars, SiYuan has built a significant following among knowledge workers who want something between Obsidian (offline-only, file-based) and Notion (cloud-only, proprietary). The main limitation is that because it uses a custom database format rather than plain Markdown files, portability requires exporting.