Cortex.md is a Chromium extension that turns every page you save into plain markdown on your disk — categorized, cross-linked, and graphed by managed AI included in your plan. No lock-in. Just a folder you can open in Obsidian.
Suppose, in the next 30 years, a tiny implantable mesh becomes available that lets you exchange information with computers as fast as you can think.
A whole-brain interface would let humans access the cloud as readily as we now access our own memories. We'd think a question, and the answer would arrive — not on a screen, but inside our heads.
Cortex.mdCapture is one keystroke. Everything downstream — readability, markdown conversion, AI categorization, link extraction — runs locally in the extension's service worker.
Hit ⌘⇧S on any page, or right-click any text. Mozilla Readability strips the chrome.
Turndown produces faithful markdown with frontmatter — title, source, capture time, tags. Lands in inbox/.
Captures get tagged, categorized, and moved out of the inbox — Auto or Manual. Powered by your monthly credits.
Cross-references between notes form a force-directed graph. Click any node to jump in.
Cortex.md writes to a folder you pick. Open it in Obsidian. Grep it. Commit it to a private git repo. Move it to a different machine. The vault is not a database we hold for you — it's just files.
Every wikilink becomes an edge. The side panel renders a force-directed view of the whole vault — clusters surface naturally, orphans surface what needs linking.
Two AI surfaces, both included in your plan. Ask answers questions from notes you've already captured, with wikilink citations. Auto-research types a topic, and Cortex.md writes a fully-linked note from the open web — entities, concepts, citations and all.
Three threads ran through what you read on BCIs in spring 2026:
1. Bandwidth is the bottleneck. Current invasive electrodes max out around a few thousand neurons; [[Neuralink and the Brain's Magical Future]] argues a useful "whole-brain interface" needs ~10⁶ channels — a four-order-of-magnitude gap.
2. Read is easier than write. Decoding intent from motor cortex is largely solved; closed-loop stimulation that feels like a thought rather than a buzz remains open ([[Brain-Computer Interfaces]], §3).
3. Substrate independence is the long bet. [[Whole-Brain Emulation]] reframes BCIs as the gradual half of a Ship-of-Theseus migration off biological wetware.
Cortex.md only sees a page when you ask it to. The extension uses activeTab + scripting instead of host permissions, so it can't read a page until you tell it to.
Best-in-class models, included in your plan. Hit your monthly credit cap and we pause — no surprise bills.
One folder, one keystroke, and a brain-shaped graph of everything you've read. Start free — upgrade when you need more credits.