Hi HN,<p>I'm Dom, a solo founder. I built Second Brain to solve a common issue I had with AI chats: the knowledge disappears. There’s no structure, no memory, and no way to reuse or build on them.<p>So I built a tool that combines AI chat with a visual, interconnected knowledge system.<p>Key features:
- Save AI responses into editable docs (Notion-style Pages).
- AI Visual board with multiple content & chat nodes (like Miro meets ChatGPT).
- Add and chat with YouTubes, TikToks, Audio, PDFs, GitHub repos, Looms, websites, etc.
- Organize using Projects and Smart Tags — then chat with full contexts.
- Chrome extension for saving anything in 1 click.
- Built on GPT-4.1, Claude Sonnet 4, Grok 3, and DeepSeek R1.<p>Privacy: user data is never stored on AI providers or used for training.<p>Would love your feedback or ideas.
Demo: <a href="https://youtu.be/4prRwP2BjxM" rel="nofollow">https://youtu.be/4prRwP2BjxM</a><p>Happy to answer any questions about the tech or why I built it!<p>— Dom