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This quickstart helps you write a server-side script that bridges USDC between two EVM-compatible blockchains. The examples in this quickstart use Base Sepolia and Arc Testnet, but you can use any supported EVM chains as the source or destination.

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Prerequisites

Before you begin, ensure that you’ve:

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Step 1. Set up the project

This step shows you how to prepare your project and environment.

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1.1. Set up your development environment

Create a new directory and install Bridge Kit and its dependencies:
Shell
# Set up your directory and initialize a Node.js project
mkdir bridge-kit-quickstart-transfer-base-to-arc
cd bridge-kit-quickstart-transfer-base-to-arc
npm init -y

# Install Bridge Kit and tools
npm install @circle-fin/bridge-kit @circle-fin/adapter-viem-v2 viem typescript tsx

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1.2. Initialize and configure the project

First, initialize the project. This command creates a tsconfig.json file:
Shell
# Initialize a TypeScript project
npx tsc --init
Then, edit the tsconfig.json file:
Shell
# Replace the contents of the generated file
cat <<'EOF' > tsconfig.json
{
  "compilerOptions": {
    "target": "ESNext",
    "module": "ESNext",
    "moduleResolution": "bundler",
    "strict": true
  }
}
EOF

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1.3. Configure environment variables

Create an .env file in the project directory and add your wallet private key, replacing {YOUR_PRIVATE_KEY} with the private key from your Base Sepolia (or any EVM) wallet.
If you use MetaMask, follow their guide for how to find and export your private key.
Shell
echo "PRIVATE_KEY={YOUR_PRIVATE_KEY}" > .env
This use of a private key is simplified for demonstration purposes. In production, store and access your private key securely and never share it.

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Step 2. Bridge USDC

This step shows you how to set up your script, execute the bridge transfer, and check the result.

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2.1. Create the script

Create an index.ts file in the project directory and add the following code. This code sets up your script and transfers 1 USDC from Base Sepolia to Arc Testnet:
Using other EVM chains? Change the chain values in kit.bridge() and ensure your source wallet has USDC and both wallets have native tokens.
TypeScript
// Import Bridge Kit and its dependencies
import { BridgeKit } from "@circle-fin/bridge-kit";
import { createViemAdapterFromPrivateKey } from "@circle-fin/adapter-viem-v2";
import { inspect } from "util";

// Initialize the SDK
const kit = new BridgeKit();

const bridgeUSDC = async (): Promise<void> => {
  try {
    // Initialize the adapter which lets you transfer tokens from your wallet on any EVM-compatible chain
    const adapter = createViemAdapterFromPrivateKey({
      privateKey: process.env.PRIVATE_KEY as string,
    });

    console.log("---------------Starting Bridging---------------");

    // Use the same adapter for the source and destination blockchains
    const result = await kit.bridge({
      from: { adapter, chain: "Base_Sepolia" },
      to: { adapter, chain: "Arc_Testnet" },
      amount: "1.00",
    });

    console.log("RESULT", inspect(result, false, null, true));
  } catch (err) {
    console.log("ERROR", inspect(err, false, null, true));
  }
};

void bridgeUSDC();
Customize your bridges to collect a fee, use the Circle Forwarding Service, or estimate gas and provider fees before bridging, proceeding only if the cost is acceptable.

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2.2. Run the script

Save the index.ts file and run the script in your terminal:
Shell
npx tsx --env-file=.env index.ts

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2.3. Verify the transfer

After the script finishes, find the returned steps array in the terminal output. Each transaction step includes an explorerUrl. Use that link to verify that the USDC amount matches the amount you transferred. The following code is an example of how an approve step might look in the terminal output. The values are used in this example only and are not a real transaction:
Shell
steps: [
  {
    name: "approve",
    state: "success",
    txHash: "0xdeadbeefcafebabe1234567890abcdef1234567890abcdef1234567890abcd",
    data: {
      txHash:
        "0xdeadbeefcafebabe1234567890abcdef1234567890abcdef1234567890abcd",
      status: "success",
      cumulativeGasUsed: 17138643n,
      gasUsed: 38617n,
      blockNumber: 8778959n,
      blockHash:
        "0xbeadfacefeed1234567890abcdef1234567890abcdef1234567890abcdef12",
      transactionIndex: 173,
      effectiveGasPrice: 1037232n,
      explorerUrl:
        "https://testnet.arcscan.app/tx/0xdeadbeefcafebabe1234567890abcdef1234567890abcdef1234567890abcd",
    },
  },
];