Logseq
logseq.com
Logseq is a privacy-first, open-source knowledge management tool focused on personal outlining and daily journaling. Operating on a local-first architecture, all notes are stored as plain Markdown or Org-mode files directly on your local hard drive. It features bidirectional linking, card-based flashcards for spaced repetition, PDF annotation tools, and dynamic graph visualizations to build a personal second brain.