The Ethereum Foundation and the Open Anonymity Project have launched zkAPI, a system that lets users prepay for AI and other metered services without tying their billing identity to every request they make. It's been live on Ethereum mainnet since October 1.
The design uses zero-knowledge proofs paired with disposable API keys, so the account paying for a service and the account consuming it don't have to be the same thing. That's a meaningful change for anyone who's ever topped up an AI endpoint with a card attached to their real name.
How the two sides get separated
Metered services have a structural problem. To pay, you need an account. To use the API, that same account gets logged against every call. zkAPI breaks that chain in two places: the proof shows a payment is valid without revealing who made it, and the disposable key lets a user burn through requests without carrying a persistent identifier.
Neither the Foundation nor the Open Anonymity Project has published the cryptographic specifics beyond that, so there's no way yet to judge how strong the unlinkability actually is in practice. "Zero-knowledge" is a broad label, and the guarantees depend entirely on how the proof system is wired up.
Live since October 1
The system is already on Ethereum mainnet, not a testnet. That matters. Mainnet deployments cost real gas and expose real contracts, which usually means the team considers the code stable enough to leave running unattended. It also means anyone can go interact with it today rather than wait for a grant announcement.
What's less clear is who's actually using it. Neither organization has put out usage numbers, and there's no list of integrated AI providers or metered services on the record. Without that, the launch is more of a proof of concept than a working product at scale.
The catch neither group has spelled out
There is a catch. The provided details don't say what it is. That's frustrating, and it's the kind of gap that usually gets filled by speculation on crypto Twitter within hours.
Plausible candidates exist — prepayment models can require a deposit that ties up capital, disposable keys can complicate refunds and chargebacks, and zk proof generation isn't free computationally. But none of that is confirmed. Treat any specific claim about the tradeoff as unverified until the Foundation or the Open Anonymity Project puts it in writing.
The honest read: two well-known Ethereum-adjacent organizations shipped an anonymous billing layer for metered APIs, put it on mainnet, and left the fine print for later. That's a real thing to watch, not a finished product to adopt.
What to watch for
The next concrete signal is documentation. Until the project publishes the proof construction, the key lifetime rules, and which AI providers are actually integrated, there's no meaningful way to evaluate whether zkAPI's anonymity holds up when someone tries to break it. The Foundation hasn't given a timeline for that.
