Ethereum’s zkAPI is now live on mainnet, giving users a way to pay for AI and other API services without revealing their billing identity. The Ethereum Foundation announced on Thursday that the system, built with the Open Anonymity Project, has moved from proposal to working implementation.
How zkAPI Works
Users deposit funds into an Ethereum vault. They then use zero-knowledge proofs to prove they have enough credit to pay for API requests without revealing which deposits belong to them. That proof shows the balance exists without exposing the account behind it.
The system issues short-lived API keys with predefined spending limits. Requests are sent directly to the AI provider, while usage is settled separately through the payment layer. The project has also released a local client and software development kit, along with a browser-based AI chat implementation.
The February Proposal
The launch follows a February proposal by Ethereum Foundation researcher Davide Crapis and Ethereum co-founder Vitalik Buterin for ZK-based API usage credits. That design has now become a working mainnet implementation.
The concept was presented as a way to give users private, prepaid access to AI and other metered APIs. The proposal described the design; the launch puts it on chain.
What It Hides
The system hides billing identity. Users can prove they have paid without showing who paid.
What It Does Not Hide
zkAPI does not hide request contents or network metadata from providers. Users can still potentially be linked across sessions through IP addresses, timing or information contained in their requests.
That limitation is worth noting. Privacy is not absolute here — it is a trade between what the system protects and what it does not. The design chooses to protect identity while leaving content exposed.
The Local Client
The project has released a local client and software development kit alongside the browser-based AI chat implementation. These tools give developers a way to build applications that use the payment system without exposing their own users’ identities.
The browser-based chat is a demonstration of what the full stack looks like in action.
Why This Matters
Private prepaid access matters for users who want to keep their consumption separate from their identity. An API payment that reveals nothing about the payer changes the economics of a service that charges per request.
The system also supports short-lived API keys with spending limits. That combination — prepaid, private, capped — is the design goal the proposal set out to achieve.
The Limitation
The system does not hide request contents or network metadata from providers. That means users can still be linked across sessions through IP addresses, timing or information contained in their requests.
That is a real constraint, not a minor detail. Anyone building on top of zkAPI needs to understand what it preserves and what it leaves open. The design tradeoffs are explicit: identity is protected, but content is not.
A Working Mainnet Implementation
The February proposal was a design. The mainnet launch is a running system. The difference matters for anyone who wants to use it today rather than wait for a whitepaper.
| Feature | What zkAPI Does | What It Does Not Do |
|---|---|---|
| Billing Identity | Hides it | Shows it |
| Request Contents | Not hidden | Exposed |
| Network Metadata | Not hidden | Exposed |
| Spending Limits | Supports them | Does not apply |
| API Keys | Issues them | Does not issue them |
The launch delivers on the promise of the February proposal. The system is live on mainnet, which means it is no longer a proposal. It is a working implementation.
For users, the takeaway is simple: there is now a way to pay for AI services without exposing your identity. Whether that is worth the tradeoffs depends on what you are trying to hide and what you are willing to expose. The system does not hide everything, but it hides the most sensitive thing — the payer’s identity.
Source material: “Ethereum’s zkAPI brings privacy-preserving API payments to mainnet,” Cointelegraph.
Get the Notebook.
The day's best stories and every fresh verdict, in plain English, in your inbox by seven. One email a day, no more.