Obsidian is a local-first Markdown note-taking app developed by a Canadian team. The core app is free and it is known for bidirectional links and the knowledge graph. With 1000+ community plugins and paid Sync/Publish add-ons, it is a popular choice for personal knowledge management and a second brain.
Neo4j is the world's leading graph database company, founded in 2007 by Emil Eifrem and others, headquartered in San Mateo, California, USA, offering a native graph database, the Cypher query language, and GraphRAG AI capabilities widely used in fraud detection and knowledge graphs.
Foam is a free, open-source personal knowledge management tool built on VS Code, using local Markdown files and bidirectional links to build a knowledge graph, completely free under the MIT license, suited to technical users familiar with VS Code and Git.
Anytype is a local-first, offline-capable open-source knowledge management platform featuring end-to-end encryption and an object-relationship model, currently free, ideal for privacy- and data-sovereignty-focused users.
Logseq is an open-source local-first note-taking app launched in 2021 by a US team, built around outlining and bidirectional links; notes are stored as Markdown files locally with PDF annotation and whiteboard support, a popular choice for building personal knowledge bases.
Founded by May Habib in 2020 and headquartered in San Francisco, Writer is an enterprise generative AI platform offering proprietary Palmyra models, an AI writing assistant, brand knowledge base and compliance rule engine for regulated industries.