Cortex — Local Second Brain

About

Cortex remembers the web pages you read, so you can find them later by what they said, not just by URL.

Type "that article about AI agents from last week" or "which site mentioned remote work in Charlotte" — Cortex finds it. Ask questions about anything you've read and get answers with citations to the original sources.

WHAT MAKES CORTEX DIFFERENT

- Runs 100% on your device. The AI model is bundled with the extension — Cortex makes zero network calls during normal use.
- Free forever. No accounts, no subscriptions, no data collection.
- Open source. Audit the code yourself if you want to verify the privacy claims.
- Works on every page you read, automatically. No bookmarking required.

HOW IT WORKS

After install, browse normally. Cortex extracts the readable text from pages you visit and stores it in your browser's local database. Press Cmd+Shift+K (Mac) or Ctrl+Shift+K (Windows) anywhere to open the search overlay.

Three modes:

SEARCH — Find pages by content, not just URLs. Hybrid keyword + semantic search returns relevant pages even when you don't remember exact words.

ASK — Get synthesized answers with inline citations. "Summarize what I read about React server components" returns a paragraph with linked sources.

TODAY — A daily digest of what you read yesterday or in the last week. Top topics, notable findings, a narrative summary of your day.

PRIVACY

Indexed text stays in your browser. The embedding model is bundled — no remote model downloads. Sensitive sites (banking, healthcare, password managers, email) are skipped automatically. You can pause indexing or block specific domains anytime.

Optional Cloud Chat (off by default): if you want richer answers for complex questions, you can add your own Google Gemini API key. When enabled, only the retrieved snippets needed to answer your question are sent to Gemini — never your full library.

KEYBOARD SHORTCUTS

- Cmd+Shift+K (Mac) / Ctrl+Shift+K (Windows): Open search overlay
- Alt+Shift+C: Alternative shortcut if the primary conflicts
- ↑↓: Navigate results
- Enter: Open result
- Cmd/Ctrl+Enter: Open in background tab
- Esc: Close overlay