Minibits

Minibits is a mobile Cashu wallet built by Misovan. It runs on Android and iOS and lets users hold ecash from multiple mints, pay over Lightning, and send tokens directly to other users through Lightning addresses, nostr contacts, or plain Cashu tokens. The app is available in English, Slovak, Spanish, and Portuguese.

The wallet integrates with Lightning in the usual ways (LNURL pay, LNURL withdraw, Lightning addresses), and also supports nostr-native flows: you can send ecash over NIP-17 encrypted DMs (sealed and wrapped via NIP-44) to any nostr contact. Tokens can be locked to a recipient's public key, and a payment can be prepared while offline for the recipient to claim later.

Minibits also supports NFC tap-to-pay. A user taps their phone to a Numo point-of-sale terminal or to another Minibits wallet, and the wallet writes a Cashu token back to the NFC tag to settle the payment (the payer can stay offline during the tap). A short demo shows the flow.

Every wallet gets a persistent name@minibits.cash Lightning address routed through the project's own server, which also handles zap notifications and Nostr Wallet Connect delivery so payments reach the app even when it's backgrounded.

Minibits keeps the "bearer" property of ecash: tokens live on the device, not on a server, and can be exported, imported, or transferred between phones while keeping the same wallet address.

Why fund it?

Cashu needs well-maintained wallets on the platforms people actually use. A fast mobile client that supports the full stack of modern Cashu NUTs (payment requests, WebSockets, cached responses, v4 token format, multi-mint balances) tests the protocol under real-world load and surfaces bugs that only appear on constrained devices.

OpenSats supported Minibits in the seventh wave of Bitcoin grants in September 2024 and renewed the grant in the sixteenth wave. For a detailed review of what the project shipped, see the Advancements in Ecash impact report.

What's next?

Android builds ship through Zapstore. iOS is now publicly available to EU users through Freedom Store (cooperation with the Vexl foundation), with TestFlight still serving the rest of the world. Recent work added the compact v4 token format, animated QR codes for large tokens (NUT-16), payment requests (NUT-18), WebSocket subscriptions for instant balance updates (NUT-17), cached responses for crash-safe payments (NUT-19), offline transfers, P2PK-locked tokens, token export/import with device-to-device migration, and a challenge-response auth flow between the wallet and the Minibits server inspired by NIP-42.

Upcoming work focuses on more reliable Nostr Wallet Connect flows (especially under Android's background process limits), continued iOS polish, hardening offline transactions based on real-world usage from places like Cuba, and keeping the wallet aligned with new Cashu NUTs as they ship.