Cashu enables offline Bitcoin payments with zero internet needed

Cashu, an open-source ecash protocol, demonstrated NFC tap-to-pay on July 7, enabling Bitcoin transfers between phones without either party needing internet.

Calle, the protocol's creator, showcased the feature in a demonstration that showed two phones transferring Bitcoin-backed tokens via a simple tap, according to the project's documentation.

The system uses bearer-style ecash tokens that function like physical cash — whoever holds them owns them, with no account or identity verification needed at the moment of transfer. The tokens are minted by third-party "mints" that hold Bitcoin or Lightning Network deposits as backing. When a user wants to spend, they tap their phone against another device, and the NFC chip transfers the token from one wallet to another.

Because the mint creates the token in one step and the user spends it in a separate step, transactions happen without on-chain fees or Bitcoin transfer delays. The separation between token issuance and spending is the key design choice that enables offline functionality.

Several wallets have already started integrating this NFC transfer capability. Minibits, a mobile wallet, supports Cashu token transfers. Numo, a point-of-sale application, has also been building around the protocol, meaning merchants could accept these tap-to-pay transfers in physical retail settings. Earlier work in 2025 laid the groundwork, including NFChat for NFC transfers between wallets and improved offline receiving capabilities in Nutstash, another Cashu-compatible wallet.

The protocol's design traces its lineage to David Chaum's original eCash concept from the 1980s. Chaum, widely considered the godfather of digital cash, envisioned a system where electronic payments could be as private as handing someone coins. His company DigiCash built this in the 1990s, but it was ahead of its time and eventually went bankrupt. Cashu takes Chaum's blueprint and wires it into Bitcoin's infrastructure. Funding for continued development comes partly from OpenSats, which provides long-term support for open-source Bitcoin projects.

Because ecash tokens are bearer instruments, they carry strong privacy guarantees. The mint that issues a token does not necessarily know who ends up spending it. Transactions between users leave no on-chain trace — no public ledger entry, no wallet address to monitor, no transaction graph to analyze.

The trust model deserves scrutiny. Cashu mints are trusted or semi-trusted entities. Users deposit Bitcoin and receive ecash tokens in return, relying on the mint to hold the backing funds and honor redemptions. That is a different trust assumption than holding Bitcoin in a self-custodial wallet — more like a bank note backed by gold reserves.

The practical implications for areas with limited or unreliable internet access are significant. A payment system that works offline via NFC could unlock use cases that Lightning alone cannot reach, potentially expanding Bitcoin's utility as a medium of exchange in regions with poor connectivity.

This article is for informational purposes only and does not constitute investment advice.