SiYuan

SiYuan is an open-source, privacy-first personal knowledge management system. Its distinctive feature is fine-grained, block-level referencing: any block can be linked to or embedded elsewhere, with two-way links, custom attributes and SQL query embeds. Editing is Markdown WYSIWYG, and the project describes itself as a workspace where humans and AI agents work together. It is local-first and self-hostable.

The editor supports block-style writing, list outlines, block zoom-in, very large documents, math formulas, charts, flowcharts and Gantt charts. Web clipping, PDF annotation links, flashcards with spaced repetition, a database table view, Tesseract OCR and multi-tab split-screen layouts are included. You can export blocks and embeds, standard Markdown with assets, or PDF, Word and HTML. AI writing and Q and A chat can use the OpenAI API, and template and JavaScript or CSS snippets allow customization.

SiYuan is AGPL-3.0 licensed and available as desktop apps, mobile apps for Android, iOS and HarmonyOS, an installation package, a package manager, and Docker, Kubernetes, Unraid and TrueNAS hosting. A command line interface and an app market for extensions exist. Most features are free, even for commercial use.