Obsidian

Obsidian is a free, local-first note-taking and knowledge management app that stores all your notes as plain Markdown files on your device. There is no proprietary database, no required account, and no cloud dependency. You connect ideas using bidirectional links, and Obsidian visualises those connections as an interactive graph so you can see how your knowledge fits together. For AI builders, Obsidian matters because its local-first architecture makes it one of the strongest foundations for building a personal AI knowledge base, where your notes become the context layer for any LLM you choose to run, including fully local models.

How Obsidian works

Obsidian treats your notes as a vault: a folder of plain .md files that live on your machine. The app reads from and writes to that folder, but the files themselves are always accessible from any text editor. Here is how the core system works:

• Markdown files: Every note is a standard Markdown file. You write in plain text with formatting, code blocks, images, and tables. Because the format is open, your notes never get locked into a proprietary container.
• Bidirectional links: Wrap any word or phrase in [[double brackets]] to create a link between notes. Obsidian tracks links in both directions, so each note shows what other notes point to it. This turns a flat list of files into a connected knowledge graph.
• Graph view: Obsidian renders your entire vault as an interactive node map. Each note is a dot, and each link is a line. You can zoom, filter by tag, and click any node to open the note, giving you a visual picture of how your ideas connect.
• Plugins: The core app is deliberately minimal. The community plugin library adds over 2,700 extensions, covering everything from daily notes and spaced repetition to AI chat and local LLM integration.
• AI plugins: Plugins like Smart Connections and Obsidian Copilot connect the app to external LLMs or local models. They index your vault and let you ask questions, find related notes, and generate content grounded in what you have already written.
• Sync options: Obsidian Sync is the official paid sync service. Alternatively, many users self-host sync through iCloud, Dropbox, or a private WebDAV server, since the files are plain text and sync anywhere.

What you can build with Obsidian

• Local AI knowledge base: Store research notes, paper summaries, and project documentation in your vault. Use the Smart Connections plugin with a local model via Ollama to chat with that knowledge base entirely offline, with no data leaving your machine.
• Prompt engineering library: Maintain a structured vault of prompts, tested variations, and observed outputs. Link each prompt to the use case, model, and outcome. Use graph view to spot patterns across your prompt experiments over time.
• Developer second brain: Keep architecture notes, decision logs, code snippets, and meeting summaries as linked Markdown files. Because the vault is just a folder, you can open it in VS Code, commit it to a Git repo, and version-control your knowledge the same way you version-control your code.
• Research synthesis system: Write literature notes for each paper or article you read. Link them to project notes and atomic idea notes. Over time, Obsidian’s graph view surfaces connections between sources you had not noticed, speeding up the synthesis process for reports and papers.
• Personal task and project manager: Use the Tasks plugin to track to-dos across notes. Combine it with daily note templates to build a simple project management system where every task links back to its context, and you query open items from anywhere in the vault.
• AI workflow scratchpad: Build a vault section dedicated to AI experiments. Log the context, model, prompt, and result for each run. Link related experiments and use Obsidian Copilot to surface relevant past runs when you start a new one.
• Team documentation hub (self-hosted): Publish a subset of your vault to a website using Obsidian Publish, or host the vault on a shared drive for a small team. Combine with a shared plugin setup to give the whole team AI-assisted search over the same knowledge base.