The Ethereum Foundation and the Open Anonymity Project have launched zkAPI on Ethereum mainnet, a protocol intended to let users pay for AI services and other metered APIs without connecting their payment identity to individual requests. Users deposit funds into the ZkAPIVault contract and retain a private balance on their device. A browser-generated zero-knowledge proof establishes that sufficient funds are available and unspent, allowing zkAPI to issue a temporary API key with a spending cap. Once the key expires, a usage receipt determines the deduction from the private balance, while a nullifier prevents the same funds from being spent twice. The design separates payment data from requests but does not conceal prompts, IP addresses or timing information from service providers. The Open Anonymity Project introduced OA Chat on September 25, 2026, and the Ethereum Foundation promoted zkAPI on October 2. The protocol originated in a proposal by Davide Crapis and Vitalik Buterin, while the Open Anonymity team built its client, server, smart contracts and browser integration.