Open source alternatives to Obsidian

What Obsidian does

Obsidian is a desktop and mobile app for personal notes and knowledge bases. Notes are stored locally as plain Markdown files in a folder called a vault, so they work offline and can be opened with any text editor. Notes link to each other, backlinks and an interactive graph show the connections, and Canvas lays out notes and ideas on an infinite board. Thousands of community plugins and themes extend the app. The app is free for personal and commercial use; Obsidian Sync, with end-to-end encryption, version history and shared vaults, and Obsidian Publish for websites are paid add-ons.

Why people look for an alternative

Obsidian already avoids many of the issues that push people away from hosted note services: data stays on your device in an open format, and the vendor says the app collects no telemetry. The reasons to look elsewhere are narrower.

• Closed source. The license overview states that the company owns the code in the app. It cannot be audited, modified or continued by others if development stops, even though your notes remain readable Markdown.
• Paid sync and publishing. The official way to sync between devices and to publish notes is a paid subscription.
• A different model of notes. Some people want block-level references, outliner editing, a deep note hierarchy, structured queries or built-in self-hosted sync, which are central to other tools.
• Personal by design. Collaboration is limited to shared vaults through Sync.

What to compare in an alternative

1. File format. Logseq’s file-based version writes plain Markdown or Org-mode files, closest to an Obsidian vault. SiYuan, Trilium Notes and Logseq’s new DB version store notes in a database and export Markdown.
2. Linking model. Logseq and SiYuan reference and embed individual blocks; Trilium places notes in a tree and lets one note appear in several places.
3. Sync. Trilium syncs through your own server at no cost. SiYuan charges for sync, including to your own S3 or WebDAV storage. Logseq’s official sync is paid and currently invite only for DB graphs, but file-based graphs are plain folders you can copy as you like.
4. Mobile apps. Logseq and SiYuan have mobile apps; Trilium relies on its mobile web interface or community apps.
5. Extras. SiYuan includes flashcards, PDF annotation and SQL queries; Trilium has canvases, mind maps and scripting; Logseq has daily journals and a plugin API.

Which one to choose

Logseq is the closest choice if you value Markdown files and daily journals, and its outliner gives fine-grained block links; be aware that its DB version is still in beta. SiYuan suits people who want block references, queries and study tools in one local app and are willing to pay for sync. Trilium Notes is the strongest option for very large knowledge bases and free self-hosted sync, with many note types and scripting, though notes live in a SQLite database. The notes and knowledge base guide covers note apps and team wikis as well.