Deposit Ether to ZKsync

Depositing assets from L1 to L2 is a fundamental step to interact with ZKsync. This guide demonstrates how to deposit ETH using the Javascript SDK, ensuring a smooth transition of assets to L2. In ZKsync, assets deposited from L1 are locked in a smart contract and corresponding representations of these assets are minted on L2, enabling fast and cheap transactions.

Prerequisites

• Node.js: Ensure you have Node.js installed. If not, download it from here.
• Private Key: Have access to a private key for the account you'll be using.
• L1 RPC Endpoint: A URL to an Ethereum node to interact with. You can find RPC endpoints for Sepolia and Ethereum mainnet on Chainlist or use a node provider like Alchemy.

Understand L1 - L2 Deposits

Depositing assets from L1 to L2 involves calling the deposit method on the L1 bridge contract. Here's a simplified breakdown of the process:

1. Locking L1 Tokens: Initially, the specified tokens on L1 are sent to the L1 bridge, where they are locked.
2. Initiating L1 to L2 Transaction: The L1 bridge then initiates a transaction to the L2 bridge, marking the start of the deposit process.
3. Minting L2 Tokens: Tokens corresponding to the deposit are minted on L2 and sent to the designated L2 address.
   • If the token contract isn’t already present on ZKsync Era, a new contract is deployed with a new L2 token address, which is derived from the original L1 address, name, and symbol.
4. Confirmation Logging: Each executed L1 to L2 transaction is confirmed with a log message sent from L2 back to L1.
5. Finalizing Deposit: Finally, the finalizeDeposit method is called on the L2 bridge to complete the deposit process, ensuring the funds are minted on L2.

This structured flow ensures a secure and orderly transfer of assets from L1 to L2, paving the way for further interactions on the Layer 2 network.

Setup Environment

Setup the node script:

mkdir deposit-scripts && cd deposit-scripts
npm init -y
npm i typescript ts-node ethers@^5.7.2 zksync-ethers@5 dotenv

Create a .env file in the project root containing your private key and the L1 RPC endpoint.

WALLET_PRIV_KEY=<YOUR_PRIVATE_KEY>
L1_RPC_ENDPOINT=<RPC_URL>

Create the Deposit Script

Create a new file deposit.ts and insert the below code:

import { Wallet, Provider, utils } from "zksync-ethers";
import * as ethers from "ethers";

// load env file
import dotenv from "dotenv";
dotenv.config();

// HTTP RPC endpoints
const L1_RPC_ENDPOINT = process.env.L1_RPC_ENDPOINT || ""; // or an RPC endpoint from Infura/Chainstack/QuickNode/etc.
const L2_RPC_ENDPOINT = process.env.L2_RPC_ENDPOINT || "https://sepolia.era.zksync.dev"; // or the ZKsync Era mainnet

// Amount in ETH
const AMOUNT = "0.00001";

const WALLET_PRIV_KEY = process.env.WALLET_PRIV_KEY || "";

if (!WALLET_PRIV_KEY) {
  throw new Error("Wallet private key is not configured in env file");
}

if (!L1_RPC_ENDPOINT) {
  throw new Error("Missing L1 RPC endpoint. Check chainlist.org or an RPC node provider");
}

async function main() {
  console.log(`Running script to deposit ETH in L2`);

  // Initialize the wallet.
  const l1provider = new Provider(L1_RPC_ENDPOINT);
  const l2provider = new Provider(L2_RPC_ENDPOINT);
  const wallet = new Wallet(WALLET_PRIV_KEY, l2provider, l1provider);

  console.log(`L1 Balance is ${await wallet.getBalanceL1()}`);
  console.log(`L2 Balance is ${await wallet.getBalance()}`);

  // Deposit ETH to L2
  const depositHandle = await wallet.deposit({
    to: wallet.address,
    token: utils.ETH_ADDRESS,
    amount: ethers.utils.parseEther(AMOUNT),
  });
  console.log(`Deposit transaction sent ${depositHandle.hash}`);
  console.log(`Please wait a few minutes for the deposit to be processed in L2`);
}

main()
  .then()
  .catch((error) => {
    console.error(error);
    process.exitCode = 1;
  });

Run the Script

Execute the script using the following command:

npx ts-node deposit.ts

Verify the Deposit

Upon running the script, you should see output similar to below, indicating the deposit transaction has been sent and is being processed on L2:

Running script to deposit ETH in L2
L1 Balance is 6539874840163375070
L2 Balance is 5712612651486983637
Deposit transaction sent 0xffb8e302430b0584e2e0104dd6295a03688c98ba7b6e9279b01dba65188cc444
Please wait a few minutes for the deposit to be processed in L2

Conclusion

By following this guide, you have successfully deposited ETH from L1 to L2 using the ZKsync Javascript SDK. This is a fundamental step towards interacting with the ZKsync Era.