Open source alternatives to Obsidian

By GitHub stars it is Memos, with 64,448 stars and a commit on 13 Nov. Choose Memos when you want quick notes you can reach from any browser and share with others, without paying for Obsidian Sync. Next come SiYuan (47,216 stars) and Logseq (45,584 stars).

Yes. The code of all 11 is public under MIT, AGPL 3.0, AGPL 3.0 or later or GPL 3.0, so you can use them with no licence fee. Running one yourself costs the server and your time to look after it, and some makers also sell a hosted plan.

Start from the job you use Obsidian for. Choose Notesnook when you want to host it yourself and keep your data on your own server. Choose Tolaria when you want open source code you can run and change yourself.

10 of the 11: Memos, SiYuan, Logseq, Notesnook, Standard Notes, SilverBullet, Beaver Notes, Zen and 2 more. Each tool's page says what it needs to run.

10 of the 11 we track had a commit in the last 30 days, among them Memos, SiYuan, Logseq and Tolaria. The quietest is Darkwrite, last changed on 15 Oct. A recent commit shows the project is kept up, not that it will stay that way.

AGPL 3.0 (5), MIT (3), AGPL 3.0 or later (1), GPL 3.0 (1), MPL 2.0 (1). MIT, BSD and Apache let you change and reuse the code freely. GPL and AGPL ask you to share your changes under the same licence when you give the software to others, and AGPL also counts letting people use it over a network.

The hosting. Obsidian's maker runs the servers for you; with an open source tool the updates, backups, security fixes and support are yours, unless you take the maker's hosted plan. Features differ too, so check what each one imports and exports before you move your data.