Cashu

Cashu distinguishes four components: wallets, mints, the public specification and bearer tokens. Its NUT specifications describe token formats and optional features, helping developers check whether two implementations support the same behavior.

For a user, the first choice is a compatible wallet and mint. Funding the mint through a Lightning invoice produces ecash tokens that can be transferred by QR code or message. The recipient redeems those tokens with that same mint. Tokens issued by one community's mint cannot simply be received as another mint's tokens; a transfer over Lightning is needed between the two systems.

What the mint and wallet each hold

The mint operates the Lightning infrastructure and holds the underlying Bitcoin. The wallet holds a claim on that issuer, rather than native Bitcoin controlled solely by a wallet key. Redemption depends on the mint remaining able and willing to pay.

Blind signatures are designed to separate issuance from later redemption in the mint's records. They do not make every payment untraceable: network metadata and the Lightning transactions at the edges can still reveal information.

Backups also depend on the chosen wallet. Clearing browser storage can erase locally held tokens. Where seed recovery is supported, keep the mint addresses as well as the seed because recovery cannot automatically discover every mint used.

The site’s Wallets section lists implementations; Protocol leads to the specifications, and Libraries covers integration tools. Cashu remains an evolving protocol, so implementation support and operator fees need to be checked for the particular wallet and mint.