You've heard that building a second brain will transform your productivity. But with dozens of apps claiming to be the perfect tool, how do you choose? After testing 15+ knowledge management apps extensively, we've identified the 7 best second brain apps that actually deliver on their promises.
This isn't just a feature list. We've used each tool for real work:research projects, writing, and daily knowledge capture:to understand where they excel and where they fall short.
What Makes a Great Second Brain App?
Before diving into the tools, let's establish what actually matters for a second brain:
- Frictionless capture : If it's hard to save information, you won't do it
- Intelligent retrieval : Finding what you saved matters more than how you organize it
- Connection discovery : The best tools help you see relationships between ideas
- Sustainable workflow : The app should work for you, not create more work
With these criteria in mind, here are the 7 best second brain apps available today.
1. Atlas : Best for AI-Powered Knowledge Management
Best for: People who want AI to do the heavy lifting of organization and retrieval
Atlas takes a fundamentally different approach to the second brain. Instead of relying on manual organization, it uses AI to automatically connect your knowledge and answer questions across everything you've saved.
Key strengths:
- Natural language search across all your content
- AI-generated connections without manual linking
- Knowledge graph visualization
- PDF and web article analysis
- Chat interface for synthesizing insights
Pricing: Free tier available, Pro from $12/month
Why we recommend it: If you've tried building a second brain before and failed because organization became a chore, Atlas removes that friction entirely. The AI handles retrieval, so you can focus on capturing and using knowledge.
2. Obsidian : Best for Power Users
Best for: Technical users who want full control and local-first storage
Obsidian has become the go-to choice for serious PKM practitioners. Its combination of local Markdown files, powerful linking, and extensive plugin ecosystem creates unmatched flexibility.
Key strengths:
- 100% local, your data stays on your device
- Bidirectional linking with visual graph
- 1000+ community plugins
- Customizable with CSS and JavaScript
- One-time purchase for sync (no subscription required for core features)
Pricing: Free for personal use, Sync $4/month, Publish $8/month
Considerations: The learning curve is real. Obsidian rewards investment but requires it. Many users spend weeks just configuring their setup before doing actual work.
3. Notion : Best for All-in-One Workspaces
Best for: Teams and individuals who want databases, docs, and wikis in one place
Notion isn't purely a second brain app, but its flexibility makes it a popular choice. The database feature lets you create custom views of your knowledge, and recent AI additions have improved search and summarization.
Key strengths:
- Powerful databases with multiple views
- Great for team collaboration
- Clean, modern interface
- Notion AI for summaries and writing assistance
- Extensive template gallery
Pricing: Free for personal use, Plus $10/month
Considerations: Notion can become a sprawling mess without discipline. It's also fully cloud-based with no offline support, which concerns some users.
4. Roam Research : Best for Networked Thought
Best for: Researchers and writers who think in connected ideas
Roam pioneered the bidirectional linking approach that many apps now copy. Its daily notes workflow and block-level references create a unique writing and thinking experience.
Key strengths:
- Block-level transclusion
- Powerful queries and filters
- Daily notes as primary capture method
- Strong academic and research community
- Real-time collaboration
Pricing: $15/month or $165/year
Considerations: Roam's interface feels dated compared to newer alternatives, and the price is steep for what you get. Development has also slowed considerably.
5. Mem : Best for AI-First Note-Taking
Best for: Users who want AI assistance without complex setup
Mem positions itself as an AI-native note-taking app. It automatically organizes your notes and surfaces relevant information without requiring tags or folders.
Key strengths:
- AI-powered organization and search
- Meeting transcription and summarization
- Smart suggestions for related notes
- Clean, minimal interface
- Calendar integration
Pricing: Free tier available, Pro from $14.99/month
Considerations: Mem is newer and less proven than established tools. Some users find the AI organization opaque:you can't always understand why notes are connected.
6. Tana : Best for Structured Knowledge
Best for: Users who want database-like structure with note-taking flexibility
Tana combines the freeform nature of note-taking with the structure of databases. Its "supertags" let you define schemas for different types of information.
Key strengths:
- Supertags for structured data
- Powerful search and filters
- Daily notes with calendar view
- AI commands for automation
- Keyboard-first design
Pricing: Free during beta, pricing TBA
Considerations: Tana is still invite-only and relatively new. The learning curve is steep, and the lack of mobile apps is a limitation.
7. Capacities : Best for Object-Based Organization
Best for: Visual thinkers who want to organize by "objects" rather than notes
Capacities offers a fresh approach where everything is an "object" with properties and connections. It's particularly good for organizing people, books, projects, and concepts.
Key strengths:
- Object-based organization (books, people, concepts)
- Beautiful graph visualization
- Daily notes with smart suggestions
- Media and content embedding
- Relatively gentle learning curve
Pricing: Free tier available, Pro from $9.99/month
Considerations: Capacities is newer and still building out features. The object model takes adjustment if you're used to traditional note-taking.
Feature Comparison Table
| Feature | Atlas | Obsidian | Notion | Roam | Mem | Tana | Capacities |
|---|---|---|---|---|---|---|---|
| AI Search | ✓ | Plugin | ✓ | ✗ | ✓ | ✓ | ✗ |
| Auto-Organization | ✓ | ✗ | ✗ | ✗ | ✓ | ✗ | ✗ |
| Knowledge Graph | ✓ | ✓ | ✗ | ✓ | ✗ | ✓ | ✓ |
| Local-First | ✗ | ✓ | ✗ | ✗ | ✗ | ✗ | ✗ |
| Mobile Apps | ✓ | ✓ | ✓ | ✓ | ✓ | ✗ | ✓ |
| Free Tier | ✓ | ✓ | ✓ | ✗ | ✓ | ✓ | ✓ |
| Collaboration | ✗ | ✗ | ✓ | ✓ | ✓ | ✓ | ✗ |
How to Choose Your Second Brain App
Choose Atlas if: You want AI to handle organization and retrieval automatically. Best for people who've tried other systems and found them too much work to maintain.
Choose Obsidian if: You want full control, local storage, and don't mind investing time in configuration. Best for technical users and privacy-conscious individuals.
Choose Notion if: You need more than just a second brain:databases, wikis, team collaboration. Best for people who want an all-in-one workspace.
Choose Roam if: You're focused on research and writing, and want powerful block-level connections. Best for academics and serious researchers.
Choose Mem if: You want AI assistance but prefer a simpler interface than Atlas's graph view. Best for meeting notes and quick capture.
Choose Tana if: You need database-like structure with the flexibility of notes. Best for organizing complex projects with many related entities.
Choose Capacities if: You think better in terms of objects (books, people, concepts) than documents. Best for visual thinkers.
The Case for AI in Your Second Brain
Traditional second brain apps require significant manual work: tagging, linking, organizing, maintaining. Most people who start with enthusiasm eventually abandon their systems because the overhead becomes unsustainable.
AI changes this equation. Tools like Atlas and Mem can:
- Surface relevant notes without manual organization
- Answer questions across your entire knowledge base
- Find connections you'd never discover manually
- Reduce the friction that causes most second brains to fail
If you've tried building a second brain before and struggled, the new generation of AI-powered tools might be worth exploring.
Getting Started
The best second brain is the one you actually use. Here's our recommendation:
- If you're new to PKM: Start with Atlas or Mem for the gentlest learning curve
- If you want control: Start with Obsidian and invest in learning the system
- If you need team features: Start with Notion and build your personal knowledge within it
Whatever you choose, start small. Capture one type of content. Build the habit. Expand from there.
Ready to build your second brain? Try Atlas free and experience AI-powered knowledge management.
Frequently Asked Questions
What is a second brain app?
A second brain app is software designed to store, organize, and retrieve personal knowledge. The term was popularized by Tiago Forte's "Building a Second Brain" methodology, which treats external tools as an extension of your memory and thinking.
Are second brain apps worth it?
Yes, if you regularly consume and need to recall information. Knowledge workers, students, researchers, and creators benefit most. The key is choosing a tool that fits your workflow and actually using it consistently.
Can I use a free second brain app?
Several excellent options have free tiers: Atlas, Obsidian (core features), Notion (personal use), Mem, and Capacities. You can build a fully functional second brain without paying anything.
What's the difference between a second brain app and a note-taking app?
Note-taking apps focus on capture. Second brain apps emphasize connection and retrieval:helping you not just store information but actually use it later. The difference is in the focus on knowledge management, not just storage.
Should I use multiple second brain apps?
Generally, no. Fragmented knowledge is hard to search and connect. Choose one primary tool and commit to it. The exception is using specialized tools that integrate with your main system.