Keys stay with you
Your identity and message keys are sealed in your operating system's keychain. They are never uploaded, never escrowed, never shown to the user interface in the clear.
Messaging where your keys
never leave your device.
Mercury is an end-to-end encrypted messenger. Your identity keys live in your computer's keychain, not on a server. The relay that moves your messages only ever sees opaque ciphertext — it cannot read what you send.
Windows 10/11 · verify the download against the published
.sha256 · see honest status below.
Why it's different
The server is blind
The relay is a dumb router for already-encrypted bytes. It forwards opaque ciphertext and content-free metadata, and has no path to decrypt anything.
No phone number
Mercury identifies you by a cryptographic account id, not a phone number or email. Nothing about your real-world identity is required to send a message.
AI is a visible guest
When an AI participant joins a conversation it is an explicit, invited principal with a scoped grant — never a hidden plaintext backdoor.
Honest status
Mercury is early and built for small-scale use first. We would rather tell you exactly what works today than overstate it — that posture is the whole point of a security tool.
- Windows first. A Windows installer is available now. macOS and Linux builds are planned but not yet published.
- Delivery is online-when-open. A message arrives when the recipient's app is running; otherwise it waits in the relay's queue until they next open Mercury. There is no background push notification for a closed app yet.
- Builds are not code-signed yet. Until a signing certificate is in place,
Windows will show an "unknown publisher" prompt on first launch. Verify the installer against
its published
SHA-256checksum. - You bring the relay. Running Mercury for a group means standing up a relay (one Docker command) and pointing a subdomain at it. Whoever hosts your group runs it.
Get started
- Download and install the Windows app above.
- Open Mercury and share your account id with the people you want to message.
- Connecting a group needs a relay to route messages — whoever runs your group stands one up with a single command, then shares its address.