Obsidian

Obsidian is a knowledge base and note-taking application that stores everything as plain Markdown files in a local folder on the user's device, which means notes remain readable, portable, and usable without the app and are not locked into a proprietary format or cloud. Its core concept is linking: notes connect to each other with wiki-style links and backlinks, and a graph view visualizes the resulting web of ideas, which suits personal knowledge management, research, and writing. Obsidian includes a canvas for spatial arrangement of notes and media, and Bases, a feature added in 2025 that turns collections of notes into filterable, formula-driven database views. Its most distinctive strength is an ecosystem of thousands of community plugins and themes that extend it into a task manager, spaced-repetition tool, kanban board, and much more. Obsidian is made by a small team and is free to use for both personal and commercial purposes, with no account required. It sells two optional paid add-ons: Sync, an end-to-end encrypted service for keeping a vault in sync across devices, and Publish, for turning notes into a public website, along with a voluntary commercial license for organizations that want to support the project.