Local-first. Backed by Git.

The local-first notebook for you, your team, and your agent.

Local files for you. Real-time sync for your team. Full context for your agent.

Download Beta for Mac
Free for personal use · macOS, Windows, Linux · Files stay on your disk
Yours

Your files. Your control.

Notes are local markdown files saved on your computer.

  • Open in any editor. Move to any tool. You're free to leave (but won't want to).
  • Works with your existing AI (Claude Code & Cowork, Codex, etc.)
~/Notes
Notes/
Trip planning/
tokyo-may.md
kyoto-itinerary.md
Reading/
2026-queue.md
highlights.md
Work/
meeting-notes.md
.git/
Built for AI

AI-native, your way.

  • Notes are .md files, comments are .comments.json sidecars — works with any AI that reads files.
  • Structured tools via a local MCP server, running on your machine.
  • Direct line from your AI to its provider. No Cortex middleman.
$ claude
> Update tokyo-may.md to put the booking deadline at the top
Your agent on your machine. Cortex never sees the prompt.
Safely Synced

Synced everywhere. Every version saved.

  • Access your notes on any device.
  • Version control backed by Git.
  • Connect with GitHub to host the repo on your own org.
history · tokyo-may.md
a1f0c2eAdd Kyoto leg + booking deadline note from Sam 2m ago
7d9b341Refactor itinerary into day-by-day blocks 3h ago
3e22a08Agent: drafted hotel shortlist (5 options) yesterday
0b14d99Initial trip outline 3 days ago
Collaborate

Shared workspace for your team & agents.

  • Real-time edits, comments, and suggestions.
  • Monitor every change your agent makes, and have it leave comments for review.
  • Control access at any level — workspace, folder, or doc.
…the booking deadline is the 14th…
SM
Sam2m ago
Should we move this up? It's the most time-sensitive thing in the doc.
AI
Cortex agentjust now
Moved. The same date appears in tokyo-may.md — want me to keep them in sync?
Familiar

The features you already know and love.

Everything you'd expect from a modern markdown editor — and the ability to customize your workspace.

  • Write with checkboxes, callouts, math, code, embeds, and tables.
  • Connect and visualize your notes with [[wikilinks]] and a graph view.
  • Make it yours — customize your workspace, sidebars, icons, and colors.
Flexible

Many ways to use Cortex.

Solo or with a team. On your computer or in the cloud. Your files don't change — only how you reach them.

Solo
Team
Local Files
Solo · Local
  • Files on your computer, accessible to your agent.
Team · Local
  • Everyone gets a local copy, backed by your GitHub repo.
  • Your team and their agents commit edits and comments through Git — no real-time editing.
  • Conflicts handled like code: Git diffs, last write wins.
Cloud Sync
Solo · Cloud
  • Nothing to install. Sign in and start writing.
  • Your files synced to the cloud, accessible from any device.
Team · Cloud
  • Real-time editing with teammates.
Why Cortex

Every note app makes a trade-off. We didn't.

Notion, Obsidian, Apple Notes, Bear, iA Writer — pick one and you give something up. Cortex is the only one that doesn't ask.

Notion Obsidian Apple Notes Bear iA Writer Cortex
Beginner-friendly — ~
Customizable (icons, emojis) ~ ~ ~ —
Local files you own — ~ ~
Git history & diffs — ~ — — —
Team + agent collab — ~ — —

A notebook you'll never have to leave.

Free for personal use. Download Cortex and start writing in 60 seconds — your files end up exactly where you'd expect them.

Download Beta for Mac Windows & Linux (coming soon)
No account required · Sync is optional · Open data, always