> ## Documentation Index
> Fetch the complete documentation index at: https://docs.renvoy.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# What is x402?

> HTTP 402 Payment Required — a standard protocol for machine-to-machine USDC payments over HTTP.

## The problem

Traditional payment flows — credit cards, invoices, subscription billing — require human identity, legal agreements, and manual onboarding. They work for people, but they break for machines.

AI agents can't get credit cards. Automated pipelines can't sign contracts. And micropayments under $1 aren't viable when card processing fees start at $0.30.

## HTTP 402: Payment Required

HTTP has had a status code for this since 1997: **402 Payment Required**. It was reserved "for future use" — and the future is now.

The [x402 protocol](https://www.x402.org/) defines a standard way to use 402 responses for real payments:

1. **Client** requests a resource
2. **Server** responds with `402` and a `payment-required` header describing the price, network, and payment address
3. **Client** signs a USDC transfer authorization (no on-chain transaction yet)
4. **Client** retries the request with the signed payment in the `X-PAYMENT` header
5. **Facilitator** verifies the signature, submits the transaction on-chain, and confirms settlement
6. **Server** returns the resource

No signup. No API keys on the client side. No invoices. Just HTTP.

## What is a facilitator?

The facilitator is the settlement engine. It:

* **Verifies** that the signed payment is valid (correct amount, correct recipient, sufficient balance)
* **Settles** the payment on-chain by submitting the transaction to the network
* **Returns** the transaction hash and settlement confirmation

The facilitator never holds funds. It submits the client's pre-signed transfer directly to the USDC contract. The merchant receives USDC in their wallet.

## Supported networks

| Network                | CAIP-2 ID                                 | Status            |
| ---------------------- | ----------------------------------------- | ----------------- |
| Base (mainnet)         | `eip155:8453`                             | Production        |
| Base Sepolia (testnet) | `eip155:84532`                            | Sandbox / Testing |
| Solana (mainnet)       | `solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp` | Production        |
| Solana Devnet          | `solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1` | Sandbox / Testing |

## Learn more

* [x402 Protocol Specification](https://www.x402.org/)
* [Getting Started](/getting-started) — try it in 2 minutes