Obsidian is a local-first note-taking and personal knowledge management application that stores all notes as plain text Markdown files on the user's own device. Because data never leaves the device by default, users retain full privacy and ownership of their content, with no dependency on cloud infrastructure to access their notes offline.

The application enables users to create rich, interconnected knowledge bases by linking notes together through wiki-style internal links. A built-in graph view visualizes the relationships between notes as an interactive network, helping users discover patterns and connections across their entire vault. Canvas, an additional built-in feature, provides an infinite, freeform workspace for brainstorming, diagramming, and organizing ideas spatially.

Extensibility is central to the Obsidian experience. Thousands of community-built plugins extend core functionality to cover use cases including task management, calendar views, kanban boards, spaced repetition, and database-style queries. A library of community themes allows users to fully customize the visual appearance of the application.

Obsidian is available on Windows, macOS, Linux, iOS, and Android. An optional Sync add-on provides end-to-end encrypted synchronization across devices with one year of version history and support for shared vaults. An optional Publish add-on lets users convert their notes into public websites with customizable themes, full-text search, and graph navigation, optimized for performance and SEO without requiring any technical configuration.