x402 Authentication

In addition to API keys, the Zapper API supports authentication via the x402 protocol. This allows you to pay for API usage on a per-request basis using USDC on Base, Polygon and Avalanche, with 0 fees and instant settlement.

Learn more about x402

Example Client

Below is an example client implementation that demonstrates how to use x402 authentication with the Zapper API:

import axios, { AxiosInstance } from 'axios';
import { createPaymentHeader, selectPaymentRequirements } from 'x402/client';
import { PaymentRequirementsSchema, createSigner, type Signer } from 'x402/types';

// Chain to use for payments (Polygon and Avalanche also supported)
const PAYMENT_CHAIN = 'base';

async function graphqlWithPayment(client: AxiosInstance, signer: Signer, query: string, variables: any): Promise<any> {
  let response = await client.post('/graphql', { query, variables });

  const paymentError = response.data.errors?.find(
    (err) => err.extensions?.code === 'PAYMENT_REQUIRED' && err.extensions?.accepts,
  );

  if (paymentError) {
    const { x402Version, accepts } = paymentError.extensions;

    const parsed = accepts.map((accept) => PaymentRequirementsSchema.parse(accept));

    const selectedPaymentRequirements = selectPaymentRequirements(parsed, PAYMENT_CHAIN, 'exact');

    const paymentHeader = await createPaymentHeader(signer, x402Version, selectedPaymentRequirements);

    response = await client.post(
      '/graphql',
      { query, variables },
      {
        headers: {
          'X-PAYMENT': paymentHeader,
          'Access-Control-Expose-Headers': 'X-PAYMENT-RESPONSE',
        },
      },
    );
  }

  if (response.data.errors) {
    throw new Error(`GraphQL errors: ${JSON.stringify(response.data.errors)}`);
  }

  return response.data.data;
}

async function main() {
  const privateKey = 'YOUR_PRIVATE_KEY';

  const signer = await createSigner(PAYMENT_CHAIN, privateKey);

  const client = axios.create({
    baseURL: 'https://public.zapper.xyz',
    headers: { 'Content-Type': 'application/json' },
  });

  const data = await graphqlWithPayment(
    client,
    signer,
    `query TokenPriceData($address: Address!, $chainId: Int!) {
      fungibleTokenV2(address: $address, chainId: $chainId) {
        symbol
        address
        priceData {
          marketCap
          price
        }
      }
    }`,
    {
      address: '0xbe19c96f5deec29a91ca84e0d038d4bb01d098cd',
      chainId: 8453,
    },
  );

  console.log('response:', data);
}

main().catch(console.error);

How it Works

1. Initial Request: Make a GraphQL request without payment headers
2. Payment Required Response: The API returns an 402 Payment Required error with payment requirements
3. Payment Header Creation: Create a payment header using your signer and the selected requirements
4. Retry with Payment: Retry the request with the payment header included

Query Pricing

The x402 protocol has no fees. API queries are priced the same as the Pay-As-You-Go plan (USD $0.001 / API credit, ~$0.003 / query). Visit our pricing page for exact query costs.

Supported Chains

The x402 authentication system supports payments on the following chains:

• Base
• Polygon
• Avalanche

Prerequisites

To use x402 authentication, you'll need:

• A private key for signing transactions
• Access to the x402 client libraries (x402/client and x402/types)
• Sufficient USDC balance on your chosen payment chain