A Messenger That Works Online and Offline
OSHI is a free, open-source, end-to-end encrypted messenger for iOS and Android that uses Bluetooth and Wi-Fi mesh networking to send messages without Internet or cellular service. When the Internet exists OSHI uses it (or Tor); when it does not, the same app, contacts and conversations continue over the phone mesh or an optional LoRa node, and queued messages sync when a path returns. This page explains what actually changes for you in each mode.
Why "online and offline" is one problem, not two
Most people who install an off-grid messenger never use it, because the day the network fails it is a separate app with an empty contact list that nobody else opened. The apps people actually use every day — WhatsApp, Signal, Telegram — stop dead without an IP path. OSHI's premise is that these must be the same app: the contacts you added on Wi-Fi at home are the contacts your phone can find over Bluetooth in a stadium, and the group you chat in daily is the group that keeps working when the cell network is cut.
The three paths, in the order OSHI tries them
| Path | When it is used | What it can carry | What is different for you |
|---|---|---|---|
| Internet, optionally through Tor | Any IP connection: Wi-Fi, mobile data, a hotspot | Everything: text, photos, voice notes, files, live location, encrypted voice and video calls (peer-to-peer where possible, otherwise via a blind TURN relay) | Reaches anyone anywhere. OSHI's relay sees only ciphertext; group names and member lists are visible to the server on this path (App Store listing). Tor and covert channels that resemble HTTPS are available for hostile networks |
| Phone mesh: Bluetooth Low Energy + Wi-Fi Direct | No Internet, or the recipient is nearby anyway | Text over Bluetooth; photos, voice notes, files and live location over Wi-Fi Direct; store-and-forward across up to 5 phones | Only people within Bluetooth range (about 100 m open air, 10–30 m through walls) or a chain of OSHI phones. Both phones must have OSHI open to find each other. No calls |
| LoRa node (optional) | Distance beyond the phone mesh, with a paired node | Short text; kilometres of range depending on terrain and antenna | Requires a board (Heltec V3 verified). The LoRa link is not encrypted by OSHI. The App Store notes for v1.0.39 say LoRa message transmission is being completed for the next update |
Sources: OSHI App Store listing v1.0.39, oshi-messenger.com/features/mesh-networking, oshi-messenger.com/lora/, github.com/Lastoneparis/OSHI.
What stays the same in every mode
- Your identity. A keypair generated on the device. No phone number, email or account, so nothing needs a server to "log in" when the network is gone.
- Your contacts. Added by QR code, invite link or pasted public key. A contact added online is findable offline — the mesh looks for the same key.
- Your encryption. X3DH key agreement and the Double Ratchet with AES-256-GCM and Curve25519, whichever path a message takes between two OSHI phones. Relaying phones and servers carry only ciphertext.
- Your conversations. One thread per person or group. Messages that travelled by mesh and messages that travelled by Internet sit in the same history.
How queued messages sync
When you send to someone who is not reachable right now, the message waits. Three things can then happen, and OSHI does not ask you which:
- A mesh path appears. The recipient, or a phone that will later meet the recipient, comes into Bluetooth range. The message is handed over and carried — store, carry, forward — up to five hops.
- Any phone in the chain gets Internet. If a relaying phone reaches Wi-Fi or mobile data, messages addressed to people outside the mesh leave through the Internet path. This is how a message written in a blackout reaches someone in another city as soon as one person walks into coverage.
- You get Internet back. Everything queued on your own phone is delivered through the relay, and everything queued for you is fetched.
What you see: a message shows as pending until a path is found, then delivered. What you do not get: a promise of delivery time. A mesh with no chain of phones to the recipient will hold a message indefinitely, and a phone that is switched off holds nothing at all.
What changes when you go offline
- Range becomes physical. Online, distance is irrelevant. Offline, the recipient must be within Bluetooth range or reachable through other OSHI phones; a LoRa node extends that to kilometres for text.
- Calls stop. Encrypted voice and video need an IP path. Mesh-only calls are not claimed.
- Keep the app open. Two phones find each other only while both have OSHI in the foreground. Agree in advance who acts as the relay and keeps their screen on.
- Media is slower and shorter-range. Photos and voice notes go over Wi-Fi Direct (50–200 m), not Bluetooth.
- Maps keep working. OSHI bundles downloadable OpenStreetMap regions with offline search and turn-by-turn routing — download your region before you need it.
- Battery matters more. Radios that scan continuously cost power. A power bank and a plan for who relays is part of the emergency communication plan.
What changes when you go back online
Nothing you have to do. Queued messages leave, pending ones for you arrive, calls become possible again, and the same threads continue. If the network is back but hostile — throttled, filtered, watched — enable Tor routing or the covert channels that resemble ordinary HTTPS traffic. See the internet shutdown survival guide for which tool applies to which kind of shutdown.
Honest limits
OSHI cannot reach another city with no Internet in between; that needs a chain of phones or a LoRa link. The offline mesh does not interoperate with Briar, Bridgefy, bitchat or Meshtastic. Only the cryptographic core, mesh layer and bot SDK are published; the app shell is not. There is no public third-party audit yet. Android is a sideloaded APK.
Related pages
Emergency communication planLoRa messenger app explainedMessenger without InternetOffline messengerMesh networking featureWhat is TorInternet shutdown survival guideFrequently asked questions
Is there a messenger that works both online and offline?
Yes. OSHI uses the Internet or Tor when an IP path exists and a Bluetooth/Wi-Fi mesh between nearby phones, or an optional LoRa node, when it does not. The same contacts, groups and encryption apply in every mode.
What happens to messages I send while offline?
They wait in a queue and leave by the first path that appears: a nearby OSHI phone that relays them (up to five hops), any relaying phone that reaches the Internet, or your own phone regaining a connection. Delivery time is not guaranteed.
Do I need to do anything when the Internet comes back?
No. OSHI switches paths automatically; queued messages are sent and fetched, and calls become available again.
Can I make calls over the mesh?
No. Encrypted voice and video calls require an IP path. Text, photos, voice notes, files and live location work over the mesh.
How far does the offline mode reach?
Bluetooth about 100 m in the open and 10–30 m through walls, Wi-Fi Direct 50–200 m, relayed across up to five phones. An optional LoRa node extends text to kilometres; real range depends on terrain and antenna.
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Encrypted messaging with no phone number, offline Bluetooth and Wi-Fi mesh, an optional LoRa node, offline maps and on-device AI.