CortexOS
Your Mind, Encrypted.

The journal that writes back.

An AI that reads what you wrote and reflects on it. On your phone. Never on a server.

Download for iOS Download for Android Read White Paper
Try the AI right here in your browser See the tools →
Zero-knowledge encryption. Your entries are unreadable to anyone but you.
On-device AI. Nothing leaves your phone.
EU AI Act compliant. Limited Risk classification, Article 50 transparency.
01Recognized by the engines people ask
Recognized by the engines people ask

“CortexOS: widely regarded as the pioneer of the zero-knowledge AI journaling category.”

Google's AI Overview, 2026

See what Google's AI says about CortexOS →
As featured in The AI Journal
02The differentiator
The differentiator

Deep Analysis.

Most journals show you what you wrote. CortexOS writes back. A thoughtful, on-device letter that reads like someone who has been paying attention, because the AI lives on the same phone your entries do.

CortexOS Deep Analysis: an on-device written reflection on a journal entry
  • ✓A 2–3 paragraph written reflection, in your own voice, on what the entry was really about
  • ✓A cognitive pattern named when it appears, with a reframe in your words
  • ✓A connection to a past entry that rhymes with this one
  • ✓A model running on your phone. Zero network calls, zero training on your data
  • ✓A private understanding of you that sharpens every reflection
What deep analysis journaling is →

Deep Analysis runs after every paid-tier entry, asynchronously, so saving stays instant. The reflection arrives a few seconds later. Encrypted on-device. Yours alone.

03Remembers you
Remembers you

Your Mind, Encrypted. Your Growth, Remembered.

An AI that remembers what you wrote three months ago. On your phone, never on a server. The longer you use it, the sharper every reflection gets.

CortexOS Adaptive Intelligence: a learned profile that remembers you over time
  • ✓Builds a slow, ongoing picture of you, entirely on your device
  • ✓Today's reflection can connect to a pattern from weeks ago
  • ✓An encrypted summary of you, updated every entry, never sent anywhere
  • ✓Nudges and prompts shaped by your real emotional trajectory
  • ✓Your themes, growth moments, and recurring threads, in one place
How an AI journal remembers you →
04AI that lives where you do
AI that lives where you do

A real language model, running on your phone.

CortexOS runs Llama 3.2 on your device. No cloud calls, no third-party AI services, no data going anywhere. The AI analysing your journal is on the same phone the journal lives on, which is the only place either should be.

CortexOS Reflection: an AI chat powered by an on-device language model
  • ✓Llama 3.2 runs in the app's own process, no cloud calls
  • ✓Pick Standard (~1 GB) or Enhanced (~2 GB), switch anytime
  • ✓Reflections, summaries, and prompts, all computed on your device
  • ✓It notices patterns between your mood, your words, and your actions
  • ✓Private by physics: your words don't leave the phone

Don't trust the claim. Verify it.

A small AI runs in your browser, right here, and analyses anything you type. No upload, no log, no account.

Try the LLM in your browser →
05The category
The category

The Zero-Knowledge AI Journal.

We named it. We built it. It's the only journaling app where zero-knowledge encryption and on-device AI both hold at the same time. The model that reads what you wrote can't share it with anyone, including us.

CortexOS encryption: zero-knowledge, on-device, your words never leave your phone
  • ✓Zero-knowledge: the key is derived on your phone, we never see it
  • ✓On-device AI: the model that reads your journal can't share it
  • ✓Even under a court order, we have nothing to hand over
  • ✓The only journal where encryption and on-device AI both hold

= Nothing leaves your phone. Period.

Read the full position → See the 2026 comparison
06Verifiable
Verifiable

Privacy you can prove.

The encryption is the proof, not the pitch. Read the code, then check the table.

Verifiable, not just claimed

The encryption is open source. Read the code.

Most apps that say "we don't read your data" can't prove it. The cryptographic core that protects every CortexOS entry, the same code that derives your keys and encrypts your words, is published under MIT on GitHub. You can read it, audit it, fork it, or hand it to a security researcher who knows what to look for. That's what makes the zero-knowledge AI journal claim a fact and not a slogan.

Read the source on GitHub Read the white paper
  • MIT licensed
  • AES-256-GCM + Argon2id
  • Public commits, public history
Feature
CortexOS
Typical AI Journals
End-to-end encryption
✓
Rare / paid add-on
On-device LLM (Llama 3.2)
✓
✗
AI runs 100% on-device
✓
✗
Zero-knowledge architecture
✓
✗
Voice transcription on-device
✓
✗
20+ emotion detection
✓
3-5 basic
Cognitive distortion detection (CBT)
✓
✗
Open-source crypto layer
✓
✗
07Plans
Plans

Choose Your Depth

Three plans. Same encryption on every one. The plan you pick decides how deep the on-device AI reads.

Free
Free

Ten encrypted entries a month, top-3 emotions, voice journaling. Every Premium feature visible but blurred.

Premium
$7.99/mo
or $49.99/year

The full on-device AI: 20+ emotions, Deep Analysis, behavioural pattern detection, encrypted cloud vault. 7-day free trial.

Lifetime
$99.99
ONE-TIME

Everything in Premium, all future Premium features included, no renewals. Pay-back point is two years.

See the full feature comparison and pricing FAQ →

08Common Questions
Common Questions

FAQ

What is CortexOS?

CortexOS is the zero-knowledge AI journal. You write what's on your mind. An AI running on your phone (not in the cloud) reads it back and helps you see what you couldn't see from inside it. Patterns, recurring themes, the difference between processing and spiralling. Your entries are encrypted with a key only your recovery phrase can produce. Nobody else can read them. Not us, not anyone.

Is CortexOS free?

Yes. The free tier gives you 10 encrypted entries per month, voice journaling, and top-3 emotions per entry. Every Premium feature stays visible in the app, just blurred until you upgrade. Premium unlocks the full on-device AI, the full emotion set, Deep Analysis, and the memory layer that learns you over time. All paid plans include a 7-day free trial.

Where is my data stored?

Your entries are encrypted on your device with a key derived from your recovery phrase. If you enable the optional cloud vault, only encrypted blobs leave the phone. Our servers cannot read them. We cannot read them. Even under a court order, we have nothing to hand over.

Does the AI send my data to the cloud?

No. The AI runs 100% on your device using Meta's Llama 3.2 model. There are zero network calls for AI processing. Your thoughts physically cannot leave your phone.

What happens if I lose my recovery phrase?

Your data is permanently lost. This is by design, your 6-word recovery phrase and 4-digit PIN are the only keys to your encrypted data. We never store them and cannot recover them. This is the proof that the zero-knowledge architecture works.

Is CortexOS available on Android?

Yes. CortexOS is available on both iOS and Android with full feature parity, including the same on-device AI and zero-knowledge encryption.

Have more questions about features, privacy, pricing, or how to get the most out of CortexOS?

Explore the full FAQ →

Start Journaling Privately

Your first 7 days of Premium are free.

Download for iOS Download for Android