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This quickstart helps you write a server-side script that transfers USDC from Ethereum to Solana using the Circle Wallets adapter.

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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

Warning for Viem users:Versions 2.40.0-2.40.2 of Viem contain a bug that causes bridging to fail when used with Bridge Kit. This bug was fixed in version 2.40.3.To avoid this issue, use version 2.39.3 or below, or version 2.40.3 or higher of Viem with Bridge Kit.
Create a new directory and install Bridge Kit with the Circle Wallets adapter and supporting tools:
Shell
# Set up your directory and initialize the project
mkdir bridge-kit-quickstart-transfer-eth-to-sol-with-circle-wallets
cd bridge-kit-quickstart-transfer-eth-to-sol-with-circle-wallets
npm init -y

# Install Bridge Kit, Circle Wallets adapter, and tools
npm install @circle-fin/bridge-kit @circle-fin/adapter-circle-wallets typescript tsx dotenv

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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 a .env file in the project directory with your Circle credentials and wallet addresses, replacing these placeholders with your value:
  • CIRCLE_API_KEY: your API key should be either environment-prefixed (for example, TEST_API_KEY:abc123:def456 or LIVE_API_KEY:xyz:uvw) or base64-encoded strings.
  • YOUR_ENTITY_SECRET: your entity secret should be 64 lowercase alphanumeric characters.
  • YOUR_EVM_WALLET_ADDRESS and YOUR_SOLANA_WALLET_ADDRESS are the wallet addresses you control through Circle Wallets. You can fetch the addresses from the Circle Developer Console or the list wallets endpoint.
Shell
echo "CIRCLE_API_KEY={YOUR_API_KEY}
CIRCLE_ENTITY_SECRET={YOUR_ENTITY_SECRET}
EVM_WALLET_ADDRESS={YOUR_EVM_WALLET_ADDRESS}
SOLANA_WALLET_ADDRESS={YOUR_SOLANA_WALLET_ADDRESS}" > .env
Warning: This is strictly for testing purposes. Always protect your API key and entity secret.

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1.4. Fund your wallets (optional)

For this quickstart, you need USDC and native tokens in your Ethereum testnet wallet and native tokens in your Solana testnet wallet. If you need USDC testnet tokens, use the Circle Faucet to get 1 USDC on the Ethereum Sepolia and Solana Devnet testnets. If you need testnet native tokens, use the Circle Console Faucet. For more information about the faucets, see Testnet Faucets.

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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 Ethereum Sepolia to Solana Devnet.
Typescript
// Import Bridge Kit and the Circle Wallets adapter
import "dotenv/config";
import { BridgeKit } from "@circle-fin/bridge-kit";
import { createCircleWalletsAdapter } from "@circle-fin/adapter-circle-wallets";
import { inspect } from "util";

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

const bridgeUSDC = async (): Promise<void> => {
  try {
    // Set up the Circle Wallets adapter instance, works for both ecosystems
    const adapter = createCircleWalletsAdapter({
      apiKey: process.env.CIRCLE_API_KEY!,
      entitySecret: process.env.CIRCLE_ENTITY_SECRET!,
    });

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

    // Use the same adapter for the source and destination blockchains
    const result = await kit.bridge({
      from: {
        adapter,
        chain: "Ethereum_Sepolia",
        address: process.env.EVM_WALLET_ADDRESS!, // EVM address (developer-controlled)
      },
      to: {
        adapter, // Use the same adapter instance
        chain: "Solana_Devnet",
        address: process.env.SOLANA_WALLET_ADDRESS!, // Solana address (developer-controlled)
      },
      amount: "1.00",
    });

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

void bridgeUSDC();
To transfer from Solana Devnet to Ethereum Sepolia, swap the from and to contexts in the bridge call.
Tip: Collect a fee on transfers and estimate gas and provider fees before a transfer, only proceeding 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: 
npx tsx 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://sepolia.etherscan.io/tx/0xdeadbeefcafebabe1234567890abcdef1234567890abcdef1234567890abcd",
  },
];