Z Messenger

Z is a messenger built on one idea: the server should know nothing.

There is no sign-up. No phone number, no email, no username, no password. Your
identity is a cryptographic key pair generated on your device the first time
you open the app — it never leaves your device unencrypted, and nobody, not
even us, holds a copy.

END-TO-END ENCRYPTED, ALWAYS
Every message and attachment is encrypted on your device with a Signal-style
double ratchet before it leaves, and only your contact's devices can decrypt
it. There is no "secret chat" mode, because every chat is the secret mode.

A SERVER THAT STORES NOTHING
Messages travel through a relay that holds only undecipherable ciphertext,
addressed to anonymous mailbox IDs, in RAM, until they're delivered — then
they're gone. Nothing is ever written to a database or a disk. A complete copy
of the server would reveal no messages, no names, and no list of users,
because none of that exists there.

ALL YOUR DEVICES, ONE IDENTITY
Link your desktop or a second phone by comparing a short safety code between
the two screens. Your chats, photos and files stay in sync across your own
devices — still end-to-end encrypted. Lost a device? Revoke it with one tap
and every contact's app immediately stops trusting it.

BUILT TO BE VERIFIED, NOT TRUSTED
• Compare safety numbers with a contact in person to rule out interception
• Disappearing messages, from 30 seconds to a week
• Encrypted attachments up to 24 MB, integrity-checked end to end
• Local vault encrypted with XChaCha20-Poly1305, key held in your device's
hardware keystore, with an optional app passphrase
• Content-free notifications: the push wake-up contains no message and no
sender — your device fetches and decrypts privately
• Published, auditable source code — signed releases with SHA-256 checksums

RUN IT YOURSELF IF YOU WANT
Don't want to use our relay? Host your own with one Docker command and point
the app at it. The full source is published for anyone to audit, and the license expressly permits personal self-hosting.

Z is for people who think privacy should be the default, not a feature.

Recent changes:
• Z is now in Spanish, and follows your device's language.
• Add someone without meeting them: send a one-time invite, then compare eight digits on a call.
• Sending no longer identifies you to the relay, and it can no longer tell who is in a group.
• Your contacts' device lists are now checked against a public transparency log.
• A device you remove stops receiving, the app no longer backs up to your cloud, and Z warns before an unencrypted relay.