Est. 2025 — A notebook that thinks back
Your mind,
faithfully kept.
Cortex is a second brain for people who think in sentences. Capture the fragment, connect it to the whole, and let your knowledge compound like interest.
Free for the first 500 notes. No credit card, no lock-in — your archive exports to plain Markdown, forever yours.
Note № 2,481 — Tuesday
A city is a second brain we built together — streets are its axons, cafés its synapses. [[urbanism]] meets [[memory palaces]]. Follow up with the piece on medieval [[cathedrals as notebooks]].
Three principles
§ 1 — Method- 01
Capture everything
A thought arrives unannounced and leaves without warning. Cortex holds the door open — one keystroke and the fragment is kept, source and all, before it evaporates.
- 02
Link as you think
Notes are not filed, they are woven. Every sentence can reach every other sentence, so your archive grows a nervous system instead of a graveyard of folders.
- 03
Resurface on time
A second brain earns its name by remembering for you. Old notes return precisely when they become relevant — in the document where they matter most.
The ledger
§ 2 — In numbers- Notes captured by our members
- 4,821,309
- Connections drawn between ideas
- 19,204,556
- Average time to file a thought
- 0.8 s
- Members who call it indispensable
- 97%
“I stopped rereading my notes years ago. Now my notes reread me — and hand me the paragraph I forgot I wrote.”
Mara Ellison — Essayist, member since 2025
Open an account with your future self.
Every note is a deposit. Every link is interest. Start your archive today — it pays out for the rest of your thinking life.
Claim your first 500 notes