Deploy your first contract

This tutorial shows you how to deploy and interact with a smart contract on ZKsync Era in less than 5 minutes. It will help you get familiar with the ZKsync smart contract development and deployment process using different tools.

In this section you will learn how to:

Build a smart contract to exchange messages with Zeek.

Deploy the smart contract to the ZKsync Sepolia Testnet.

Interact with the contract from your browser using Remix or Atlas.

Prerequisites

Before you start, make sure that you’ve configured the ZKsync Sepolia Testnet in your wallet.
Have at least 0.5 ZKsync Sepolia Testnet ETH. If you need more, use one of the faucets.

Review the smart contract code

The smart contract will store messages from users and emit events with replies from Zeek. The entire code is as follows:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract ZeekMessages {
    string[] private messages;

    // Event to acknowledge a new message
    event MessageReceived(string);

    constructor() {
        // Zeek initializes the contract with a welcome message
        emit MessageReceived("Zeek welcomes you to ZKsync!");
    }

    function sendMessage(string memory _message) public {
        messages.push(_message);

        // Acknowledge the message receipt with Zeek's reply
        emit MessageReceived("ZK is the endgame - Message received!");
    }

    // Function to count the total messages sent to Zeek
    function getTotalMessages() public view returns (uint) {
        return messages.length;
    }

    // Function to return the last message sent to Zeek
    function getLastMessage() public view returns (string memory) {
        require(messages.length > 0, "No messages sent to Zeek yet!");
        return messages[messages.length - 1];
    }
}

The Solidity smart contract contains two functions:

sendMessage stores the messages sent by users in the messages state variable.
getTotalMessages returns the number of messages stored in the smart contract.
getLastMessage returns the last message sent.

ZKsync Era is EVM compatible. You can write smart contracts with Solidity or Vyper and use existing popular libraries like OpenZeppelin, just like on Ethereum.

Compile and deploy the contract

To compile and deploy the contract you can use either Atlas or Remix:

Atlas is a browser-based IDE with an integrated AI assistant that allows you to write, test and deploy smart contracts directly from your browser. Click the button below to open the project in Atlas.

Open smart contract in Atlas

Compile and deploy the contract

Enter a name for the project and you will see the contract in the Atlas code editor. On the right side, make sure the selected network is “ZKsync Sepolia Testnet“ and click on “Deploy” to trigger the smart contract compilation and deployment.

Contract in Atlas

Behind the scenes, Atlas is using the ZKsync Era custom solidity compiler (named zksolc ) to generate ZKEVM compatible bytecode. Learn more about ZKsync custom compilers.

Once compiled sign the transaction with your wallet and wait until it's processed. You’ll see the contract in the “Deployed contracts” section. Congratulations, you’ve deployed your first smart contract to ZKsync Sepolia Testnet!

Interact with the contract

Below the contract name you can find its deployment address. The “Live Contract State” section displays the smart contract balance and the value returned by the getTotalMessages function.

Contract deployed

The “Write Functions” section contains the form to interact with the sendMessage function. Write a message, click the “Run” button and confirm the transaction in your wallet. You’ll see that the getTotalMessages is updated to 1 and getLastMessage returns the message you just sent. That means our contract is storing the messages as expected! But how can you see the replies from Zeek?

The Remix IDE is an open-source web and desktop application that supports Ethereum smart contract development and deployment, offering tools for writing, testing, debugging, and deploying smart contracts written in Solidity to EVM compatible protocols.

Enable the Remix ZKsync plugin

To deploy smart contracts to ZKsync via Remix you need to enable the ZKsync plugin.

Visit the Remix website
Click on the “🔌 Plugin Manager” button in the bottom-left corner
Search “zksync” and click on the "Activate" button.

Enable ZKsync plugin in Remix

Once activated, you’ll see a new menu item with the ZKsync logo. Click on it to see the different options to compile, deploy, and interact with smart contracts on ZKsync.

Click the button below to open the project in Remix and see the contract in the Remix code editor.

Open smart contract in Remix

Connect your wallet

Make sure your wallet is currently connected to the ZKsync Sepolia Testnet as we will use our wallet’s configured network to deploy our smart contract. In Remix, under the Environment Section, select “Wallet” and click on “Connect Wallet”.

Compile the contract

To compile the contract, click on "Compile ZeeksSecretMessages.sol". If you get a popup message requesting permissions to access ACCESS TO "WRITEFILE" OF "FILE MANAGER", click on "Accept".

Behind the scenes, Remix is using the ZKsync Era custom solidity compiler (named zksolc) to generate ZKsync VM compatible bytecode. Learn more about ZKsync custom compilers.

Deploy the contract

To deploy the contract, open the "Deploy" dropdown, check the "Verify contract" checkbox, and click on “Deploy & Verify”. Sign the transaction in your wallet and wait a few seconds until it's processed. Congratulations, you’ve deployed your first contract to ZKsync Sepolia Testnet!

Remix interact ZKsync contract

Interact with the contract

Next to the contract name you can find the address where the contract is deployed. The “Interact” section displays the forms to interact with the getTotalMessages and sendMessage functions.

Remix interact ZKsync contract

Write a message in the form, click the “sendMessage” button and confirm the transaction in your wallet. Once processed, click the getTotalMessages and check the response in the terminal, which should be 1. The getLastMessage function should also return the message you just sent. That means the contract is storing the messages as expected! But how can we see the replies from Zeek?

Check the contract in explorer

Copy the smart contract address from Atlas/Remix and search it via the ZKsync Sepolia Testnet explorer. You’ll see the contract has a transaction from the message you just sent.

Contract in ZKsync explorer

The status will be “Processed” on ZKsync Era and “Sending” on Ethereum. Learn more about the transaction lifecycle on ZKsync.

In the “Contract” tab you’ll see the contract source code as Atlas and Remix automatically verified the contract for us. When a smart contract is verified in a block explorer, it means that the source code of the contract has been published and matched to the compiled version on the blockchain enhancing transparency, as users can review the contract’s source code to understand its functions and intentions.

Finally in the “Events” tab, you’ll see the replies from Zeek as these are emitted as events in our smart contract.

Contract events in ZKsync explorer

ZK is the endgame ✌️

Takeaways

EVM-compatibility: ZKsync Era is EVM-compatible and you can write smart contracts in Solidity or Vyper as in Ethereum.
Custom compilers: smart contracts deployed to ZKsync Era must be compiled with the customs compilers: zksolc for Solidity and zkvyper for Vyper.
Browser-based IDEs: Existing tools like Atlas and Remix use ZKsync custom compilers under the hood.

Next steps

Continue learning by deploying an ERC20 token to ZKsync.
Join the ZKsync developer community in Discord where you can ask any questions about this tutorial in the #dev-quickstart channel.
Join our GitHub Discussions Community to help other devs building on ZKsync or share your project.

Overview

Learn how to interact with ZKsync Era

Create an ERC20 token

In this tutorial you'll build and deploy an ERC20 token to ZKsync Sepolia Testnet