Roam Research

Roam Research is a note-taking tool for networked thought. Instead of organising notes in folders, you write in daily notes and connect ideas with bidirectional links, so every page automatically shows everywhere it is mentioned.

This approach helps researchers, writers and students discover connections between ideas over time and build a rich knowledge graph. Roam supports block references (reusing a single paragraph in many places), outlining, queries and a graph overview of your database. It became one of the tools that popularised the "tools for thought" and second-brain movement.

Good fit if you: think in connections and want a flexible, link-first system for research and long-term thinking.
Less ideal if you: want a polished app with built-in AI and offline-first storage; tools like Obsidian or Reflect may suit better.

Pricing: paid subscription, with a free trial.