SiYuan is an open-source, 📝local-first note-taking app for 📝personal knowledge management, built around 📝Markdown editing, 📝block references, 📝bidirectional links, databases and multi-device sync. Its site states that data is stored entirely on the user's device and that it uses end-to-end encryption. SiYuan runs on Windows, macOS and Linux, has Android, iOS and HarmonyOS apps, and can be deployed on a server with Docker.
SiYuan's README describes it as a privacy-first personal knowledge management system supporting fine-grained block-level reference and WYSIWYG Markdown editing. Its feature list adds list outlines with block zoom-in, a database table view, flashcard 📝spaced repetition, web clipping, PDF annotation links, export to PDF, Word and HTML, an API, JavaScript and CSS snippets, and a community marketplace. AI writing and question-and-answer chat connect through the OpenAI API, and the site lists continued writing, translation, abstract extraction, brainstorming and grammar correction among its AI uses. As of November 2026, the GitHub repository describes the project as a self-hosted knowledge workspace where humans and AI agents work together. The code is published under the GNU Affero General Public License v3. The README states that most features are free, even for commercial use, and the pricing page lists Free, PRO Features and Subscription plans as of November 2026.