# x402-sdk

**GitHub:** [fastxyz/fast-sdk](https://github.com/fastxyz/fast-sdk/blob/main/README.md)

## What You Can Do

* **Pay-per-request APIs** — charge for individual API calls using HTTP 402
* **No accounts needed** — just sign and pay
* **Multi-chain** — Fast (instant), Arbitrum, Base, Ethereum

## Installation

```bash
npm install @fastxyz/x402-client @fastxyz/x402-server @fastxyz/x402-facilitator
```

## Packages

| Package                     | Description                        | GitHub                                                                                        |
| --------------------------- | ---------------------------------- | --------------------------------------------------------------------------------------------- |
| `@fastxyz/x402-client`      | Sign and pay for 402 content       | [→ GitHub](https://github.com/fastxyz/fast-sdk/blob/main/packages/x402-client/README.md)      |
| `@fastxyz/x402-server`      | Protect routes, verify payments    | [→ GitHub](https://github.com/fastxyz/fast-sdk/blob/main/packages/x402-server/README.md)      |
| `@fastxyz/x402-facilitator` | Verify signatures, settle on-chain | [→ GitHub](https://github.com/fastxyz/fast-sdk/blob/main/packages/x402-facilitator/README.md) |

## How It Works

The x402 protocol is HTTP-native. On the **server side**, you add payment middleware to your routes — unprotected requests receive a `402 Payment Required` response with payment details. On the **client side**, the SDK handles the full flow: receive the 402, sign a payment, attach proof, and retry — all in one call.

For complete setup instructions, runnable code examples for both server and client, and protocol details, see the individual package READMEs linked above or the [Fast SDK monorepo on GitHub](https://github.com/fastxyz/fast-sdk).


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