Trilium Notes

Trilium Notes is a hierarchical note-taking application that stores knowledge as a tree of notes you can nest, link and tag. Notes can hold rich text, code, Mermaid diagrams, tables and attachments, attributes let you describe them consistently, scripts can automate repetitive edits, and a web clipper saves pages you find while browsing.

People use it for research, project notes, meeting minutes and personal wikis, with the tree giving long-lived archives a structure that flat note apps struggle with.

Running it yourself keeps that archive on your own disk, costs nothing per user, and the export options produce a portable backup you can restore into any instance.