Bridge Kit

Quickstart: Transfer USDC from Base to Ethereum

This quickstart guide helps you write a script that transfers USDC from Base to Ethereum.

Before you begin, ensure that you've:

Installed Node.js v22+ and npm
Created an Ethereum Sepolia wallet and Base Sepolia wallet. You will fund these wallets in this quickstart.

The sections in this step demonstrate how to prepare your project and environment.

Create a new directory and install Bridge Kit and its dependencies:

Shell

# Setup your directory and initialize a Node.js project
mkdir bridge-kit-quickstart-transfer-base-to-eth
cd bridge-kit-quickstart-transfer-base-to-eth
npm init -y

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

First, initialize the project, which 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

Create a .env file in the project directory and add your wallet private key, replacing {YOUR_PRIVATE_KEY} with the private key for your Ethereum Sepolia wallet. (You can find and export your private key in MetaMask.)

Shell

echo "PRIVATE_KEY={YOUR_PRIVATE_KEY}" > .env

For this quickstart, you need both USDC and native tokens in your Ethereum testnet wallet and native tokens in your Base testnet wallet. If you need USDC testnet tokens, use the Circle Faucet to get 10 USDC in your Ethereum testnet wallet.

Use the following faucets to get testnet native tokens in your wallets:

The sections in this step demonstrate how to set up your script, execute the bridge transfer, and check the result.

Create an index.ts file in the project directory and add the following code. This code sets up your script and transfers 10 USDC from Base to Ethereum:

Typescript

// Import Bridge Kit and its dependencies
import "dotenv/config";
import { BridgeKit } from "@circle-fin/bridge-kit";
import { createAdapterFromPrivateKey } 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 = createAdapterFromPrivateKey({
      privateKey: process.env.PRIVATE_KEY as string,
    });

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

    // Execute the transfer using the same adapter for both source and destination chain
    const result = await kit.bridge({
      from: { adapter, chain: "Base_Sepolia" },
      to: { adapter, chain: "Ethereum_Sepolia" },
      amount: "10",
    });

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

void bridgeUSDC();

Save the index.ts file and run the script in your terminal:

Shell

npx tsx index.ts

After your script completes, find the returned steps array in the terminal output. Each transaction step includes an explorerUrl that you can visit 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://sepolia.etherscan.io/tx/0xdeadbeefcafebabe1234567890abcdef1234567890abcdef1234567890abcd",
    },
  },
];

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Quickstart: Transfer USDC from Base to Ethereum

Prerequisites

Step 1. Set up the project

1.1. Set up your development environment

1.2. Initialize and configure the project

1.3. Configure environment variables

1.4. Fund your wallets (optional)

Step 2. Bridge USDC

2.1. Create the script

2.2. Run the script

2.3. Verify the transfer