Offline Messenger — Messaging With No Signal At All

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. OSHI does not require a phone number, email address, or account.

An offline messenger is an app that can deliver a message when your phone has no Internet and no cellular service. Instead of sending the message to a server, it hands it directly to another phone nearby over Bluetooth or Wi-Fi, and that phone can pass it on again. This page explains exactly how OSHI does that, what the real numbers are, what works fully offline, and what still needs a connection.

How OSHI works offline, step by step

1. Discovery. With OSHI open, your phone advertises itself over Bluetooth Low Energy and listens for other OSHI phones. On iOS this uses Apple's Multipeer Connectivity framework; on Android it uses BLE plus Wi-Fi Direct. No pairing dialog, no hotspot to join.
2. Encryption first. Before anything leaves your phone, the message is encrypted for the recipient with the Double Ratchet (X3DH key agreement, AES-256-GCM, Curve25519). The relay phones never hold a key.
3. Direct delivery. If the recipient is within range, the ciphertext goes straight to them. Short text goes over BLE; photos, voice notes and files switch to Wi-Fi Direct, which is far faster.
4. Relay. If the recipient is out of range, the packet is handed to a nearby OSHI phone with a hop counter. OSHI allows up to five hops. Each relay stores the encrypted packet and forwards it when it sees another OSHI phone (store-and-forward), until it reaches the recipient or the hop limit.
5. Sync when online. The moment any phone in the chain gets Internet, OSHI can also deliver over the Internet, Tor, or a covert channel that looks like ordinary HTTPS. Conversations stay consistent whichever path won.

What works with no connection at all

• One-to-one and group text messages with nearby OSHI users.
• Photos, voice notes, small files and live location over Wi-Fi Direct.
• Adding a contact by scanning a QR code in person — no server registration is involved, so this works on a plane.
• Offline maps: downloadable OpenStreetMap regions with search and turn-by-turn routing.
• The on-device AI assistant (translation, rewriting, smart replies, Q&A) — it runs locally and sends nothing anywhere.
• Reading your history: everything is stored encrypted on the device.

What still needs some connection

• Reaching someone who is not nearby. A message to a friend in another city waits until one of the phones in the mesh gets Internet.
• Voice and video calls. They are end-to-end encrypted and peer-to-peer where the network allows, but they need an IP path; calls over a Bluetooth-only mesh are not something we claim.
• Downloading map regions and AI models. Do this at home before you go; afterwards they work offline.
• Group metadata. When the Internet path is used, group names and member lists are visible to the OSHI server, as our App Store listing states. Message contents are not.

Battery

Bluetooth Low Energy is designed to advertise and scan for hours on little power; that is the layer OSHI keeps on. Wi-Fi Direct, which costs more, is switched on only while a photo or file is being transferred. The practical advice is simple: keep the app open when you want to relay for others (iOS throttles background Bluetooth heavily), and carry a power bank on a long day. The App Store listing is explicit that both phones need OSHI open to find each other.

How OSHI differs from other offline messengers

OSHI is an alternative to Bridgefy, Briar, Meshtastic and bitchat for offline communication, and to Signal for private messaging. Briar is audited and fully open source but Android-only. Bridgefy has the largest install base but is closed source and needs Internet on first launch. Meshtastic reaches kilometres but requires a LoRa radio per person and carries text only. bitchat is public-domain and relays up to seven hops but has no Wi-Fi transport, calls or maps. OSHI's combination is iOS and Android, Bluetooth plus Wi-Fi, five hops, photos and files, calls, offline maps and on-device AI — with the honest caveats that its app shell is not open source and it has not yet been independently audited. The full table is on the best offline messenger page.

Before you need it

Install OSHI on every phone in your group, add each other by QR code while you are together, and test it once in airplane mode. A mesh you set up after the network goes down is a mesh nobody else has joined yet.

Frequently asked questions