Obsidian
obsidian.md
A local-first Markdown note-taking app that stores notes as plain text on your device — with bidirectional wiki links, a graph visualization of note connections, and 1,500+ community plugins.
Why it is useful
One of the few note apps that keeps your data as plain Markdown files with zero vendor lock-in — your notes work in any text editor and survive any company shutdown. The bidirectional linking and graph view reveal connections between ideas you didn't consciously make. The plugin ecosystem means you can build almost any personal knowledge management workflow on top of it. Core features are free.