One product. Two perspectives.
Protect Your Conversations.
Keep the Outside World Out.
No phone number. No email required. No third-party connections by default.
Your conversations stay inside City of Hats, protected by advanced security and post-quantum cryptography.
Signal Double Ratchet · ML-KEM-768 · AES-256-GCM
Access Codes
Hidden channels. Revealed by your code.
Channel Seal
Seal a channel until your chosen time.
PRIVATE BY DESIGN · OPEN TO INSPECTION
Don't just trust
our security.
Understand it.
Explore the cryptography, device protections and privacy controls behind every Hat conversation.
No phone number or email required.
Explore all specifications & capabilities
A closer look at the mechanisms and controls that make up City of Hats. Availability follows the supported client, content type and required setup.
Beyond the encrypted message
Meet your Hat
Your identity.
On your terms.
A Hat is your private identity inside City of Hats. Give it a memorable phrase. Create one for a specific exchange. Decide how long a temporary Hat stays around.
Create your HatA Hat of your own.
Your private point of contact. Share your Hat ID or QR code, keeping your phone number and email to yourself.
Create a HatEasy to remember.
Give your Hat a phrase people can remember and type. A simpler way to reach the same private identity.
Explore Phrase IDHere for a reason.
Gone on a schedule.
An identity for a specific exchange. Choose a supported lifetime and review its expiration before sharing.
No phone number. No email required.
Illustrative identities. Temporary-Hat durations vary by plan.How it works
Start a private channel.
In three steps.
Create your Hat.
Choose a username or phrase (PhraseID). Create a Hat for your work.
Connect with a colleague.
Share its ID or QR code with a colleague to start a private channel.
Use Controlled Sharing.
Message, call and share files. Choose how sensitive content can be opened.
Beyond the message
More control.
When you need it.
Hide a channel.
Keep selected channels out of sight. Enter your Access Code to reveal them.
Explore Access CodesSeal until later.
Choose when a channel reopens—for both participants. No early unseal.
Explore Channel SealSend with control.
Choose how a sensitive file opens, who can open it, or how a PDF is signed.
Explore security modesExplore all 9 security modes
Available modes depend on the content, device and required setup.
Viewing & protection
- View OnceOne image view or file download.
- Sealed FilePIN locked. Share the PIN separately.
- Verified Eyes OnlyBiometric verification before opening.
Access conditions
- GeoLockRequire the recipient to be in your chosen area.
- NFCLockRequire a tap of their registered NFC Hat.
- VoiceLockRequire voice verification.
Document workflows
- Verified Digital SignatureRequest a certificate-backed PDF signature.
- Signature RequestSend a PDF to be signed and returned.
- Certified SendProtected PDF viewing with an access and acknowledgment record.
Controls vary by content and device. See the feature pages for availability and limits.
Try it with a colleague
Start free.
Upgrade when you need more.
City of Hats is free. Premium is optional for higher limits.
Start messaging free- A Hat for your professional identity
- Hat-to-Hat messages, calls and files
- Browser, iPhone, Android and Windows
Premium is optional. Explore higher limits
Before you start
Questions before
you start?
Find a quick answer, or explore the details.
Review security evidenceDoes it replace my everyday messaging app?
You can keep using your everyday tools. City of Hats gives sensitive work a dedicated place with separate messaging identities and deliberate controls for channels, images and files.
What do Access Codes do?
They keep selected channels hidden until you enter your code to reveal them. Your code is personal—you do not send it to the other participant. Behavior varies by platform. Check availability and how it works on your device.
What does Channel Seal do?
It restricts a channel for both participants until the time you choose. There is no early unseal. Sealing does not erase saved content. Read the details and limits.
Do I need a phone number or email address?
No. Choose Username & passphrase to create your account without either. Email and social sign-in are optional alternatives. Keep your passphrase safe.
Does the other person need City of Hats?
Yes. Both people use City of Hats for Hat-to-Hat messaging. They can join in a browser without downloading an app and create an account with a username and passphrase.
How is messaging protected?
Hat-to-Hat message, file and call content is protected between supported clients. SMS, MMS and telephone calls use carrier networks and are not end-to-end encrypted. Encryption does not protect an already-compromised device, prevent all recipient copying or remove every operational connection record. Read the Security Evidence Center for the published architecture and limits.
Your next confidential conversation
Create your Hat.
Give sensitive work its own channel.
Invite a colleague, try a private conversation,
and explore the controls that make City of Hats different.