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

Free diagramming editor (formerly diagrams.net) for flowcharts, network, UML and architecture diagrams, available as web app, desktop app and integrations

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

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