Obsidian

Obsidian is a note-taking and knowledge management app that stores notes as plain Markdown files on your own device. Users write and link notes together to build a personal knowledge base - sometimes called a second brain - that can be explored through links, backlinks and a visual graph of connections. Its local-first design is the defining choice. Notes are ordinary text files in a folder you control, not records in a company's database, so they remain readable with any editor, work offline, and are not locked into a proprietary format. That gives users confidence that years of notes will outlast the app itself, and it appeals strongly to privacy-conscious people, researchers, writers and developers. The linking model encourages networked thinking. Typing double brackets creates a link to another note, backlinks show every note that references the current one, and the graph view visualises how ideas connect. Canvas provides an infinite board for arranging notes and media spatially, and properties, tags and powerful search help organise large vaults. Extensibility is a major strength. A very large community has built plugins and themes that add task management, spaced repetition, calendars, databases, kanban boards, integrations and much more, so Obsidian can be shaped into almost any workflow. The core app is free to use, and the company earns revenue from optional paid services: Obsidian Sync for encrypted syncing across devices and Obsidian Publish for turning notes into a website. The trade-offs follow from the flexibility. A blank vault and endless plugins can lead to time spent configuring rather than writing, real-time collaboration is limited compared with cloud tools, and syncing without the paid service requires setting up an alternative. Alternatives include Notion for collaborative docs and databases in the cloud; Logseq, an open-source outliner with local files; Roam Research, which popularised bidirectional linking; Bear and Apple Notes for simple writing; Evernote for traditional note capture; and Capacities and Tana for object-based knowledge management. Choose Obsidian when you want a personal knowledge base you fully own and can customise without limits.