An introduction to x402
What is x402?
x402 is an open payment protocol that embeds payment into standard HTTP requests. A service returns machine-readable payment terms with HTTP 402; the client pays, retries the request, and receives the resource with a receipt.
Updated July 29, 2026A concise definition: HTTP requests can carry commercial terms.
A conventional paid API starts with account registration, a payment method, a subscription, and a long-lived API key. x402 brings price discovery, payment authorization, and resource delivery into a standard HTTP exchange.
It does not turn HTTP itself into a blockchain. HTTP carries the payment requirement and proof; the terms specify the asset, network, recipient, and settlement method.
How does an x402 request complete?
The client requests a resource exactly as it would call an ordinary API. If payment is required, the service responds with 402 Payment Required and structured terms such as amount, asset, network, and recipient.
- 1Request
An agent or application asks for a paid resource.
- 2Quote
The service returns HTTP 402 with machine-readable terms.
- 3Authorize
The client checks the price, network, and its own policy.
- 4Pay
The client creates payment proof and retries the same request.
- 5Deliver
The service verifies settlement and returns the resource and receipt.
A unified payment method changes more than checkout speed.
Agents can discover tools at runtime and purchase search, data, model inference, or compute one request at a time. Services no longer need a pre-existing account relationship before software can transact.
An API can become a programmable good that is purchased on the first request instead of a subscription product that requires an account and sales funnel. Value exchange gains a shared interface similar to information exchange.
x402 explains how to pay. LavoLoop decides whether payment is allowed.
The protocol cannot decide whether a particular agent is trusted, how much it may spend today, which service it may pay, or when a risky transaction requires a person.
LavoLoop sits between an agent and a user-owned wallet. Before signing, it enforces identity, budgets, service permissions, per-payment limits, human approval, and idempotency, then records the complete decision trail.
Common questions about x402
01Is x402 a cryptocurrency?+
No. x402 is a protocol for negotiating payment. Settlement can use supported networks and assets; LavoLoop's public environment currently uses Base Sepolia and test USDC.
02Why not use API keys and subscriptions?+
They remain useful for established relationships, but they do not fit agents that discover a service and buy a single request at runtime. x402 gives that exchange a common interface.
03Can an agent spend without limits once it has a wallet?+
It should not. A payment rail needs a control plane. LavoLoop enforces hard budgets, service permissions, amount limits, and human approvals before signing.
04Can I try it now?+
Yes. The public LavoLoop console demonstrates agents, budgets, approvals, payments, and audit history on a test network without moving production funds.