Ethereum's zkAPI has gone live on mainnet, turning the earlier proposal for zero-knowledge API payments into a practical implementation for private, prepaid access.
The Ethereum Foundation announced on Thursday that zkAPI has launched on the Ethereum mainnet. Developed in collaboration with the Open Anonymity Project, the system enables users to pay for AI and other API services without exposing their billing identity.
According to Vittorio Rivabella, AI coordinator for the Ethereum Foundation's dAI team, users first deposit funds into the Ethereum vault, then use zero-knowledge proofs to demonstrate they have sufficient credit to pay for API requests without revealing which deposits those funds belong to.
A direct use case of this system is paying for AI usage without linking payments to user identities. zkAPI issues short-term API keys with predefined spending limits. Prompts are sent directly to the AI provider, while usage fees are settled separately through the payment layer. The project has also released a local client, software development kit, and a browser-based AI chat implementation.
This launch implements the API usage quota scheme based on zero-knowledge proofs proposed in February by Ethereum Foundation researcher Davide Crapis and Ethereum co-founder Vitalik Buterin, turning this design into a functional mainnet implementation.
When this concept was introduced, it was envisioned as a way to provide private, prepaid access to AI and other pay-per-use APIs. However, zkAPI does not conceal the prompt content or network metadata from the service provider, meaning users may still be linked across sessions through IP addresses, timestamps, or information contained in the requests.