Cairn: AI Second Brain — Save Pages, PDFs & YouTube, Then Ask

Cairn is your AI second brain, right inside the browser. You read hundreds of pages every week — and lose most of them. Bookmarks pile up, tabs vanish, and what you learned scatters. Cairn keeps it. COLLECT — one click saves the page you're on (or hit Ctrl+Shift+S, or right-click → Save page to Cairn). Articles, PDFs, text selections, even YouTube videos (Cairn reads the transcript). Every save gets a short summary and tags, written by AI, filed automatically. RETRIEVE — ask your library in plain language: "what did I save about hybrid search?" Cairn answers from your own saves, with numbered citations that link back to the exact source — never from the open web. Video answers deep-link to the exact timestamp. CONNECT — related saves cluster into named trails, so research sessions stay together. Saving something on a topic you've touched before? Cairn tells you what it connects to. Older saves resurface when they become relevant again. PRIVATE BY DESIGN • Your library lives in your browser (IndexedDB) — no account, no tracking, no Cairn servers holding your content. • Bring your own API key (OpenAI, Anthropic, Ollama, or any OpenAI-compatible endpoint) — pages you save go directly from your browser to your provider. • Or get Cairn Pro: one license key, models included, $4/month. Our relay forwards requests and stores no content. • Encrypted export/import (AES-256) for backup and sync between machines. Obsidian export included. Free version is fully functional with your own key. Type "cairn" in the address bar to search your library from anywhere. Stack what you know.