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

# How-to: Add nanopayments to an x402 seller

> Add gas-free nanopayments to your x402 resource server alongside standard onchain payments

## Overview

* Add nanopayments to an existing `x402ResourceServer` so it offers gas-free
  payments alongside your current payment flows.
* Your existing payment setup continues to work unchanged. The server includes
  nanopayment options in its `402` responses in addition to the options your
  facilitator already supports, and buyers choose whichever method they have
  funded.

## Prerequisites

Before you begin, ensure you have:

* An existing x402 seller using `@x402/express` or `@x402/core` with
  `x402ResourceServer`.
* [Node.js](https://nodejs.org/) v18+ installed.

## Steps

### Step 1. Install the SDK

```shell theme={null}
npm install @circle-fin/x402-batching @x402/evm
```

### Step 2. Add `BatchFacilitatorClient` to your server

Add `BatchFacilitatorClient` alongside your existing `HTTPFacilitatorClient`.
Each facilitator handles a different payment type -- your existing facilitator
continues to handle standard onchain payments, and `BatchFacilitatorClient`
handles Gateway payments:

```ts theme={null}
import { x402ResourceServer } from "@x402/express";
import { HTTPFacilitatorClient } from "@x402/core/server";
import {
  BatchFacilitatorClient,
  GatewayEvmScheme,
} from "@circle-fin/x402-batching/server";

const server = new x402ResourceServer([
  new HTTPFacilitatorClient({ url: "https://facilitator.example.com" }),
  new BatchFacilitatorClient(),
]);
```

### Step 3. Register `GatewayEvmScheme`

Replace `ExactEvmScheme` with `GatewayEvmScheme`. `GatewayEvmScheme` extends
`ExactEvmScheme`, so standard onchain payments continue to work. It also
preserves the `extra` metadata (such as `verifyingContract`) that Gateway
clients need for EIP-712 signing:

```ts theme={null}
server.register("eip155:*", new GatewayEvmScheme());
await server.initialize();
```

After initialization, the server's `402` responses include Gateway nanopayment
options in the `accepts` array alongside any options your existing facilitator
supports.

<Tip>
  If you don't have an existing onchain payment setup or are a new seller, you can
  add onchain payment support by connecting to an existing x402 facilitator using
  `HTTPFacilitatorClient`. See the [x402 documentation](https://docs.x402.org/)
  for a list of available facilitators.
</Tip>

### Step 4. Route through a custom facilitator (optional)

If you run your own x402 facilitator that supports Gateway (see
[facilitator integration](/gateway/nanopayments/howtos/facilitator-integration)),
you can route payments through it instead of connecting to Circle Gateway
directly. Use `facilitatorUrl` with `createGatewayMiddleware`:

```ts theme={null}
import { createGatewayMiddleware } from "@circle-fin/x402-batching/server";

const gateway = createGatewayMiddleware({
  sellerAddress: "0xSELLER_ADDRESS",
  facilitatorUrl: "https://your-facilitator.com",
});
```

### Step 5. Check your balance and withdraw

After buyers pay for your resources, funds accumulate in your Gateway balance.
Use `GatewayClient` to check your earnings via the
[Get Token Balances](/api-reference/gateway/all/get-token-balances) API endpoint
and withdraw via the
[Create Transfer Attestation](/api-reference/gateway/all/create-transfer-attestation)
API endpoint:

```ts theme={null}
import { GatewayClient } from "@circle-fin/x402-batching/client";

const client = new GatewayClient({
  chain: "arcTestnet",
  privateKey: process.env.PRIVATE_KEY as `0x${string}`,
});

const balances = await client.getBalances();
console.log(`Available: ${balances.gateway.formattedAvailable} USDC`);
console.log(`Total: ${balances.gateway.formattedTotal} USDC`);
```

Withdraw to your wallet on the same blockchain or to a different one:

```ts theme={null}
await client.withdraw("50");

await client.withdraw("50", { chain: "baseSepolia" });
```

<Note>
  Gateway handles settlement automatically. When you call `settle()` in the
  middleware, the payment is submitted for batched processing. Your Gateway
  `available` balance increases after the batch settles onchain.
</Note>

### Step 6. Verify the integration

The server's `402` responses should now include Gateway options alongside
standard options. Check the `accepts` array for entries with:

```ts theme={null}
extra.name === "GatewayWalletBatched";
```

If both standard and Gateway entries are present, the server is correctly
offering both payment methods.

## See also

* [Use nanopayments with x402](/gateway/nanopayments/howtos/x402-integration)
  for a summary of all integration paths
* [x402 buyer integration](/gateway/nanopayments/howtos/x402-buyer) for the
  client-side counterpart
* [SDK reference](/gateway/nanopayments/references/sdk) for `GatewayEvmScheme`
  and `BatchFacilitatorClient` API details