Directory

Apple's built-in notes app for Mac, iPhone, iPad and iCloud.com with folders, tags, attachments, handwriting, shared notes and on-device search

Open-source, outliner-based knowledge base storing notes as local Markdown or Org-mode files with block references, queries and a graph view

Open-source learning management system used by universities and schools for courses, assignments, quizzes, grading and forums, self-hosted or via MoodleCloud

Local-first Markdown note-taking app with bidirectional links, graph view and a large community plugin ecosystem; optional paid Sync and Publish