What is ecash (Cashu, Fedimint)?

Ecash works like digital cash notes backed by bitcoin and issued by a "mint." Payments are cheap and very private, because the mint can't see who pays whom.

Cashu mints are usually run by one operator. Fedimint mints are run by a group of guardians, often from a local community. Either way, the mint holds the real bitcoin, so if it disappears, so do your notes. Ecash is best for small amounts, and notes can be swapped to and from Lightning.