Obsidian

Obsidian is a free note-taking app that stores notes as plain Markdown files on your own device, so they work offline, stay private and never lock you in. Notes link to each other into a personal wiki shown as an interactive graph, Canvas offers an infinite space for diagrams, and thousands of community plugins and themes reshape the app. Designers keeping a research archive or knowledge base can add paid Sync, with end-to-end encryption and a year of version history per note, or Publish for public sites.