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

# Introduction

# Introduction to X402 Echo Merchant

The x402 Echo Merchant is a free, live x402-powered merchant you can use to test any x402 client end‑to‑end.

It behaves like a real merchant: it advertises payment requirements, verifies your payment, settles it, and fulfills the request. The only difference is economic: every token you send is refunded immediately and PayAI covers the network fees. This gives you production‑like behavior with zero cost.

## At a glance

* **Live URL**: [https://x402.payai.network](https://x402.payai.network)
* **Who it’s for**: Developers building or validating x402 clients
* **What happens**: You send a payment → the request is fulfilled → your tokens are refunded → fees are paid by PayAI

## Why use it

* **Fast iteration**: Validate your x402 client integration without deploying your own merchant.
* **Zero cost**: All tokens are refunded and PayAI pays on‑chain fees.
* **Realistic flow**: Exercise discovery, verification, retry with `X-PAYMENT`, and settlement just like a production merchant.
* **Multi‑network coverage**: Test on the networks supported by x402 without juggling faucets or balances.

## How it fits into the x402 flow

1. Your client requests a protected resource at the Echo Merchant.
2. The Echo Merchant responds with `402 Payment Required` and payment requirements.
3. Your client constructs a Payment Payload and retries with the `X-PAYMENT` header.
4. The Echo Merchant verifies and settles the payment, then fulfills the request.
5. The response includes `X-PAYMENT-RESPONSE` (base64 JSON) you can decode for details.

## Related examples

* TypeScript clients: [Axios](https://github.com/payai-network/x402/tree/main/clients/typescript/axios) and [Fetch](https://github.com/payai-network/x402/tree/main/clients/typescript/fetch)
* Python clients: [httpx](https://github.com/payai-network/x402/tree/main/clients/python/httpx) and [requests](https://github.com/payai-network/x402/tree/main/clients/python/requests)

Use any of these examples and simply point the base URL to the Echo Merchant to validate your implementation.