Ethereum’s zkAPI brings privacy-preserving API payments to mainnet

The Ethereum Foundation said on Thursday that zkAPI, developed with the Open Anonymity Project, is now operational on Ethereum mainnet. The system implements a zero-knowledge approach to prepaid API payments: users deposit funds into a shared on-chain vault and produce ZK proofs to demonstrate they hold enough credit for an API call without disclosing which on-chain deposit belongs to them. One immediate application promoted by the team is private payments for AI services. zkAPI generates short-lived API keys that carry fixed spending caps; API prompts are sent directly to providers, while settlement of usage fees happens separately through zkAPI's payment layer. The design intends to unlink billing identities from API consumption by separating the payment attestations from direct provider interactions. The release includes developer tooling to ease experimentation and integration, such as a local client, an SDK, and a browser-based AI chat demo. Vittorio Rivabella, AI coordinator at the Ethereum Foundation’s dAI team, described the core flow in a foundation post, underscoring that the system turns zero-knowledge API payment ideas into an operational mainnet implementation. zkAPI follows a February proposal by Ethereum researcher Davide Crapis and co-founder Vitalik Buterin for ZK-based API usage credits; the new launch realizes that concept in usable code. The project’s authors caution, however, that zkAPI does not conceal prompt contents or network-level metadata from providers — IP addresses, timing signals, or information embedded in requests can still link activity across sessions.