Trilium Notes
FreeA hierarchical note app built for large personal knowledge bases
A community-maintained open-source note app (TriliumNext) with arbitrarily deep note trees, note cloning, scripting and full-text search. Use it locally offline or sync it via your own server.
Why we picked it
Trilium is the most capable of the hierarchical knowledge bases: 37,409 stars, AGPL-3.0, with scripting, attributes, relation maps and custom views that hold up under complex structures.
One correction worth making: the widespread claim that it is abandoned is out of date. After the original author, zadam, stepped back, the community took over. The canonical repository is now TriliumNext/Trilium, with commits still landing on 14 August 2026; the old links redirect.
The cost is the learning curve. Its customizability approaches that of a small application platform — rewarding if you are willing to tinker, heavy if you just want to jot things down.