Obsidian

Obsidian is a note-taking app that stores every note as a plain Markdown file in a local folder, called a vault. Notes link to each other with double-bracket links, backlinks are tracked automatically, and a graph view shows how ideas connect. Because the data is ordinary files on disk, notes are readable without the app, work fully offline and can be versioned or synced by any means the user chooses.

The core app is free, including for commercial use since early 2025. Its community plugin directory, with thousands of plugins and themes, covers tasks, calendars, spaced repetition, Kanban boards and much more, and the built-in Bases feature adds table-style views over note properties. An official Web Clipper extension saves pages as Markdown.

Paid add-ons are optional: Obsidian Sync (from approximately $4 per month billed annually) provides end-to-end encrypted sync across devices, and Obsidian Publish (about $8 per month) turns a vault into a website. The trade-offs are real: there is no real-time multi-user editing, no web version, and getting the most out of it depends on Markdown comfort and plugin curation, which can turn into a hobby of its own.