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Nymchat launches a messenger that keeps working when the internet does not

Free and open source, with no accounts, no phone numbers and end-to-end encrypted messages that relay phone to phone over Bluetooth when there is no network at all. Available now for Android, iOS and the web.

August 24, 2026

21 Million LLC today announced the general availability of Nymchat, an end-to-end encrypted messenger that asks for no phone number, no email address and no account — and that keeps carrying messages when the network it normally runs on is gone. Nymchat is available now as a web app at web.nymchat.app, on Android through Google Play and Zapstore, and on iOS through TestFlight.

Nearly every encrypted messenger in wide use assumes a server it can reach. Cut the connection — a shutdown, a blackout, a stadium, a subway platform, a hurricane — and the app is a blank screen. Nymchat is built so that the moment the infrastructure disappears is the moment it is most useful.

When the network goes down, the app does not

Underneath the ordinary internet transport, Nymchat runs a Bluetooth LE mesh. Nearby devices connect directly to one another and relay for each other, so a message reaches someone beyond radio range by hopping through the phones in between — up to seven hops, with each pair of devices running its own encrypted Noise XX session. There is no internet, no cell service and no infrastructure of any kind involved. Public channels and private messages both work over it, and the app picks the route on its own: online sends go over the network and fall back to Bluetooth when there is none.

Nymchat implements the same mesh protocol as Bitchat, Jack Dorsey's Bluetooth mesh app, byte for byte on the wire. The two apps are not bridged through anything — they are simply on the same mesh, discovering each other and exchanging encrypted messages directly, which makes the offline network larger for both. Bitchat is a separate project with its own owners; Nymchat is compatible with it, not affiliated with it.

The mesh runs as a full peer on Android and iOS, and as a leaf in Chromium browsers, which can connect outward to nearby phones but cannot advertise themselves.

Public rooms that are places

Nymchat's public channels are addressed by geohash: a short code for a square on the map, where each extra character narrows the area from a region to a metropolitan area to a few streets. Everyone whose device resolves to the same square is already in the same room, with no owner, no membership list, no moderator and no invitation. A built-in explorer shows a world map of where people are actually talking, with an activity heat map, a day/night terminator and the geohash grid drawn at whatever precision the zoom level warrants. Named channels — a subject rather than a place — work the way anyone would expect. Geohash channels are shared with Bitchat as well.

No account to close, and no directory to leak

There is no Nymchat account, because there is no Nymchat server that would hold one. An identity is a keypair generated on the device. The default is an ephemeral nym — minted when the app opens and discarded when the session ends — and anyone who wants a persistent identity can bring a Nostr key instead.

Ghost Mode goes further for the mesh: the signing key, the peer identifier, the advertised Bluetooth name and the nickname are all replaced with throwaway values and rotated together roughly every fifteen minutes, so a device is much harder to follow between places and sessions. On the device itself, a saved identity can be encrypted behind a password, a PIN, a passkey or a biometric, and a panic wipe destroys every local trace — encrypting each stored value under a one-time key that is then thrown away, overwriting it, and reloading to a fresh first-run state.

Encryption that is already thinking about quantum computers

Private messages and group chats are end-to-end encrypted and gift-wrapped: each copy is signed by a one-time key generated for that message alone, and its timestamp is randomly backdated by up to two hours, so the relays carrying a conversation can neither read it nor say who is talking to whom. Group chats rotate ephemeral recipient keys so that the membership list does not form a pattern a relay can watch.

Between Nymchat users, the encryption is hybrid post-quantum: the standard secp256k1 exchange stays exactly as it is, and ML-KEM-768 — the algorithm NIST standardized as FIPS 203 — keys a second layer sealed around it, so an attacker has to break both. That defeats "harvest now, decrypt later", where traffic recorded today is stored until a quantum computer can break the elliptic-curve mathematics ordinary Nostr encryption relies on. There is nothing to switch on, and nothing breaks for anyone else: messages to Bitchat users and other Nostr clients fall back to standard NIP-17. As of this writing, no other Nostr client ships it.

A complete messenger, not a survival tool

The offline mode is a fallback inside a full app rather than the whole product. Nymchat carries one-to-one and group audio and video calls, set up over encrypted events and then flowing directly between the devices taking part, with no server in the middle of the media. It has images, video and file transfer, polls, reactions, replies, disappearing messages, message translation into more than a hundred languages, six terminal-inspired themes, block lists, keyword filters and reporting.

Bitcoin payments are part of the conversation: a Lightning zap sends sats to a good post or to a person, settled between the two wallets in seconds. Nymbot, the built-in AI assistant, answers for free in any public channel and holds an end-to-end encrypted private conversation for anyone who buys credits over Lightning.

Checkable, not merely claimed

Nymchat is free software under the AGPL-3.0, and the whole thing is published — the web app and the Flutter app for Android and iOS, with no closed component to take on trust. The web build is reproducible: every asset is hashed into a manifest, a GitHub Action rebuilds each commit independently and signs build-provenance attestations, and the app's own About dialog re-hashes the files it is running, recomputes the bundle hash from what it just measured, and looks that up in the repository's signed attestations. A deployment cannot vouch for itself, and a mirror on another domain says so plainly rather than passing itself off as the official app. On Android, an APK installed from Zapstore can be checked against the SHA-256 published in a signed Nostr event.

A warrant canary, signed and anchored to a recent Bitcoin block so it cannot have been pre-signed in bulk, is published in the repository and read live by the app.

What Nymchat does not claim

The project publishes its own limits, and they belong in any accurate story about it:

Availability and pricing

About Nymchat

Nymchat — also written NYM, for Nostr Ynstant Messenger — is a free, open source messenger built on Nostr, an open protocol nobody owns. There is no account and no registration: an identity is a keypair generated on the device. Private messages and group chats are end-to-end encrypted and gift-wrapped so that relays can neither read them nor tell who sent them, with hybrid post-quantum encryption between Nymchat users. A Bluetooth mesh carries messages with no internet at all. Nymchat runs as a web app and as native Android and iOS apps, is licensed under the AGPL-3.0, and is developed by 21 Million LLC. Decentralized. Pseudonymous. Unstoppable.

Press contact

21 Million LLC — support@nymchat.app

Assets, boilerplate and fast facts: the Nymchat press kit. Technical detail behind every claim above: the knowledge base. Source code: github.com/Spl0itable/NYM.

Journalism, reviews and commentary about Nymchat need no permission. The assets on the press kit page are free to use in coverage of the app.

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