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A step-by-step guide to developing your first dApp on Avalanche


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Blockchain is most recognized as the platform that makes cryptocurrency possible. But developers are using it for much, much more than crypto.

Gaming studios are giving players real and meaningful ownership of in-game assets. Financial institutions are redefining how mortgages, loans, and investments work. Whole supply chains, from mining raw materials to delivering finished products, are tracked on a blockchain.

If you’re new to software development, or just new to blockchain, the hardest part of creating a decentralized app (dApp) might be knowing where to start. How do you get from a command line to a finished build?

This guide will give you practical advice to get you off and running.

Why Build on Avalanche?

The first consideration for beginning a blockchain project? Choosing the blockchain platform you’ll be building on. There are many public and private chains out there. We recommend Avalanche, and not just because we’re a little biased. Avalanche was built to be easier, simpler, and more cost-effective to build on than other chains.

Avalanche stands out for several reasons:

  • Developer-First Architecture: We created powerful tools like AvalancheJS and Avalanche CLI. And we’ve also made it easy to integrate with tools like Hardhat and Foundry. Avalanche supports a seamless experience for people who are used to working with any EVM-based chain.
  • Low Fees: Gas costs are consistently the lowest out of any EVM chain, making it economical for both developers and users.
  • High Throughput: Avalanche can handle thousands of transactions per second without compromising on security or decentralization.
  • Near-Instant Finality: Transactions are confirmed in under a second, which drastically improves user experience and enables real-time applications.
  • More User Control: Avalanche makes it easy to create your own sovereign L1 (layer one) chain. You can customize virtually every aspect of the chain to make it your own. This independent L1 structure makes Avalanche more scalable and efficient while giving developers more customizability.

Step 1: Setting Up Your Development Environment

It’s important to set up a clean and functional dev environment before you write your first line of code. This section will walk you through the tools you’ll need and how to configure them in order to develop, test, and deploy your first build.

Prerequisites

This guide assumes you’re already comfortable with:

  • JavaScript/TypeScript: For scripting and frontend integration.
  • Node.js & npm: The foundation for many blockchain dev tools.
  • Solidity: The main language for writing smart contracts on EVM-compatible chains.
  • Ethereum Development Basics: If you’ve used tools like Remix, Hardhat, or Truffle, you’re in good shape.

If these are new to you, we recommend reviewing basic Solidity tutorials, Deno and Node.js scripting before proceeding.

Tools Required

Let’s start by installing the core components:

  • Node.js and npm
    Download and install from nodejs.org. Recommended version: Node.js 18+ and npm 9+.

  • Hardhat or Foundry
    We’ll use Hardhat for this guide, but Avalanche is compatible with both.

    Install Hardhat globally:

npm install --global hardhat

  • Core Wallet

    Install the Core app for a fully-configurable but easy-to-use digital wallet.

  • Avalanche CLI
    A command-line tool that makes it easy to interact with Avalanche, deploy chains, and manage configurations.

    Install via npm:

npm install -g @ava-labs/avalanche-cli

  • AvalancheJS A JavaScript library for interacting with Avalanche nodes and APIs. You’ll use it to send transactions and read blockchain data.

    Install into your project:

npm install avalanche

Initializing Your Project

Once you’ve installed the above tools, start a new project:

mkdir my-avalanche-dapp
cd my-avalanche-dapp
npm init -y
npx hardhat

Choose “Create a basic sample project” and install the suggested dependencies. This sets up a working environment with Hardhat, sample contracts, and test scripts.

Configuring Avalanche Network in Hardhat

To connect Hardhat to the Avalanche network, update your hardhat.config.js file:

require("@nomiclabs/hardhat-ethers");


module.exports = {
  solidity: "0.8.19",
  networks: {
    fuji: {
      url: "https://api.avax-test.network/ext/bc/C/rpc",
      accounts: [process.env.PRIVATE_KEY]
    },
    avalanche: {
      url: "https://api.avax.network/ext/bc/C/rpc",
      accounts: [process.env.PRIVATE_KEY]
    }
  }
};

Important: Store your private key securely using environment variables or a secret manager. Never commit it to version control.

Deploying a Local Blockchain (Optional)

For local testing, Avalanche also supports deploying to a local blockchain node. While this is optional, it’s useful for advanced testing.

Start a local Avalanche node:

avalanche network start

This will spin up a local instance you can deploy to without spending testnet tokens.

Writing Your First Smart Contract

If you’ve used JavaScript before, you’ll find Solidity has a familiar syntax. It’s a contract-oriented language used to define the logic and data structure of decentralized applications running on EVM-compatible blockchains like Avalanche’s C-Chain.

We’ll start by creating a simple ERC-20 token. This is a type of token standard that is widely used in decentralized finance and other blockchain applications. By following the ERC-20 standard, your token can be easily recognized and interacted with by wallets, exchanges, and other smart contracts.

Step 1: Create the Contract

Let’s use OpenZeppelin’s secure, audited contracts as a foundation. Inside your project folder, install OpenZeppelin contracts:

npm install @openzeppelin/contracts

Now, create a new file in your project’s contracts folder:

mkdir contracts
touch contracts/MyToken.sol

Paste the following code into MyToken.sol:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.19;


import "@openzeppelin/contracts/token/ERC20/ERC20.sol";


contract MyToken is ERC20 {
    constructor(uint256 initialSupply) ERC20("MyToken", "MTK") {
        _mint(msg.sender, initialSupply);
    }
}

Let’s break this down:

  • ERC20 is an imported base contract from OpenZeppelin that defines standard token behavior.
  • MyToken inherits from ERC20.
  • The constructor takes an initialSupply and mints that amount to the deployer’s wallet.
  • “MyToken” is the name of the token and “MTK” is its symbol.

Step 2: Compile the Contract

To make sure your contract is valid and ready to deploy, run:

npx hardhat compile

If everything is set up correctly, you should see Compiled successfully.

Step 3: Write the Deployment Script

Next, you’ll write a script that deploys the smart contract to Avalanche Fuji (testnet). In your scripts directory, create a new file:

mkdir scripts
touch scripts/deploy.js

Paste the following:

const hardhat = require("hardhat");


async function main() {
  const initialSupply = hardhat.ethers.utils.parseEther("1000000"); // 1 million tokens


  const Token = await hardhat.ethers.getContractFactory("MyToken");
  const token = await Token.deploy(initialSupply);


  await token.deployed();
  console.log("MyToken deployed to:", token.address);
}


main()
  .then(() => process.exit(0))
  .catch((error) => {
    console.error(error);
    process.exit(1);
  });

This script:

  • Converts a human-readable amount of tokens to the correct format (wei)
  • Deploys the contract to the network
  • Outputs the contract address

Step 4: Configure Your Wallet & Private Key

To deploy to the Fuji testnet, you’ll need:

  1. A funded Avalanche Fuji testnet wallet (get test AVAX from Avalanche Faucet)
  2. Your wallet’s private key (never commit this to Git)

Set it in your environment:

export PRIVATE_KEY=your_actual_private_key_here

Then load it into your Hardhat config (as shown earlier).

Step 5: Deploy to Fuji Testnet

Now you’re ready to deploy your smart contract to Avalanche’s testnet:

npx hardhat run scripts/deploy.js --network fuji

After a few seconds, you’ll see your contract address. You can view it on Snowtrace (Avalanche’s block explorer for Fuji):

What You Just Did

  • Created an ERC-20 token smart contract with OpenZeppelin
  • Compiled it using Hardhat
  • Deployed it to Avalanche’s testnet
  • Minted 1 million tokens to your wallet address

You’ve taken your first step from developer to smart contract engineer. From here, you can build far more complex dApps.

Interacting with Your Smart Contract

Once your smart contract is deployed, it’s time to build a frontend that can talk to it. You’ll be able to:

  • Display token balances
  • Send tokens between wallets
  • Trigger contract functions directly from the browser

We’ll use AvalancheJS and Ethers.js for backend interaction, and Core for transaction signing.

Step 1: Install Required Libraries

From your project root:

npm install avalanche ethers dotenv
  • avalanche: Library to interact with Avalanche nodes.
  • ethers: For working with Ethereum-style contracts.
  • dotenv: To manage environment variables (like your contract address or private key).

You can also scaffold a frontend with React if you’re building a UI:

npx create-react-app my-avalanche-dapp-frontend

But for now, let’s stay focused on smart contract interaction.

Step 2: Connect to Avalanche with AvalancheJS

Here’s a sample script to interact with the C-Chain:

const { Avalanche } = require("avalanche");
const ethers = require("ethers");


// Connect to Avalanche Fuji
const ava = new Avalanche("api.avax-test.network", 443, "https");
const cchain = ava.CChain();


// Load Core wallet (or use a private key with ethers.js)
const provider = new ethers.providers.JsonRpcProvider(
  "https://api.avax-test.network/ext/bc/C/rpc"
);
const signer = new ethers.Wallet(process.env.PRIVATE_KEY, provider);


// Contract ABI and address
const tokenAbi = [
  "function balanceOf(address) view returns (uint)", // minimal ERC20 ABI
  "function transfer(address to, uint amount) returns (bool)",
];


const tokenAddress = process.env.TOKEN_ADDRESS; // deployed contract address
const tokenContract = new ethers.Contract(tokenAddress, tokenAbi, signer);

This sets up:

  • A connection to the Avalanche Fuji testnet
  • A signer (your wallet)
  • A contract instance ready to call functions

Step 3: Read from the Contract (e.g., Balance)

javascript CopyEdit async function getBalance(address) { const balance = await tokenContract.balanceOf(address); console.log(`Balance of ${address}:`, ethers.utils.formatEther(balance)); }

Step 4: Send a Transaction (e.g. Transfer Tokens)

javascript CopyEdit async function sendTokens(to, amount) { const tx = await tokenContract.transfer(to, ethers.utils.parseEther(amount)); await tx.wait(); console.log(`Sent ${amount} tokens to ${to}`); }

Core will pop up to confirm the transaction if you’re using a browser-based dApp. If running locally with a private key, transactions will be signed programmatically.

Step 5: Integrate with Frontend

You can integrate this logic into your React frontend using a simple UI:

  • An input for the recipient’s address
  • An input for the amount to send
  • A “Send” button that triggers sendTokens()

Use window.ethereum and ethers in your React app to hook into Core:

javascript CopyEdit const provider = new ethers.providers.Web3Provider(window.ethereum); await provider.send(“eth_requestAccounts”, []); const signer = provider.getSigner();

Then, instantiate your contract with the signer.

Bonus: Display Live Data

You can also call smart contract functions directly in your frontend to:

  • Display token balances
  • Render real-time data from the blockchain
  • Alert users when transactions complete

This closes the loop: from wallet → frontend → smart contract → blockchain → frontend.

You’ve now:

  • Connected to the Avalanche network using AvalancheJS and Ethers.js
  • Read from and wrote to your smart contract
  • Built the foundation for a working frontend

Core Wallet & Avalanche Network Configuration

Now that you’ve deployed your smart contract and built basic interaction scripts, the next step is ensuring users can connect their wallets and interact with your dApp.

We’ll use Core for this phase, as it’s Avalanche’s native wallet. It can function as a browser extension, mobile app, and full Web3 hub. Plus, it’s open source, so you can request new features or even create your own fork.

Here’s how to integrate Core into your dApp and configure it to connect with the Avalanche Fuji testnet.

Step 1: Install Core’s Browser Extension

You can get Core from the official site: https://core.app

Choose the browser extension for Chrome, Brave, or Firefox. Core is the preferred wallet for developing on Avalanche. It’s Avalanche-native and includes tools like address book, native token support, and dApp discovery.

Step 2: Add Avalanche Fuji Testnet to Core (If Not Already Present)

Fuji is usually preloaded in Core, but if needed, you can manually add it:

  • Open Core
  • Go to Settings > Networks
  • Add a new network:
    • Network Name: Avalanche Fuji C-Chain
    • RPC URL: https://api.avax-test.network/ext/bc/C/rpc
    • Chain ID: 43113
    • Currency Symbol: AVAX
    • Explorer: https://testnet.snowtrace.io

Once added, switch to the Fuji testnet in the dropdown.

Step 3: Connect Core to Your dApp

If you’re building a frontend, you’ll still use the same window.ethereum interface to connect to Core.

In your frontend JavaScript:

javascript CopyEdit import { ethers } from “ethers”;

async function connectCoreWallet() { if (window.ethereum) { const provider = new ethers.providers.Web3Provider(window.ethereum); await provider.send(“eth_requestAccounts”, []); const signer = provider.getSigner(); const address = await signer.getAddress(); console.log(“Connected wallet:”, address); return { provider, signer, address }; } else { alert(“Please install Core.app to use this dApp.”); } }

This allows your users to connect Core to your dApp just like they would with other wallets like MetaMask—but with native Avalanche features.

Step 4: Test Transactions with Core

Before deploying to mainnet, test all contract interactions on the Fuji testnet using Core:

  1. Request test AVAX: Visit Avalanche Fuji Faucet
  2. Send a test transfer: Use your frontend to send tokens via your deployed ERC-20 contract
  3. Monitor activity: Core.app provides a transaction history viewer and Snowtrace integration for each transaction

Step 5: Core in Production

When you deploy to Avalanche mainnet, Core will automatically detect the network. Your dApp doesn’t need to manage custom RPCs or prompt the user to add networks—it’s baked into Core’s UX.

For advanced integrations:

  • Core supports WalletConnect and deep links on mobile
  • You can integrate native Avalanche features like bridging, staking, and Interchain Messaging through the Core SDK (coming soon)

You’ve now:

  • Enabled Core as a browser extension
  • Enabled your frontend to request wallet connections and sign transactions
  • Prepared your dApp to interact with Avalanche testnet and mainnet environments

Testing on the Avalanche Fuji Testnet

Before launching your dApp into the wild, it’s essential to test every part of the system—from contract logic to frontend interactions—on a live network. The Fuji Testnet is Avalanche’s public test environment, fully compatible with the C-Chain and all other L1 chains in the network. It behaves just like mainnet, but uses test AVAX instead of real tokens.

This section will walk you through testing your smart contracts, simulating user interactions, and verifying your deployment on Snowtrace.

Step 1: Get Test AVAX

You’ll need AVAX tokens to pay for gas on Fuji. Here’s how to get them:

  1. Visit the official Avalanche Fuji Faucet: https://faucet.avax-test.network/
  2. Enter your wallet address (from Core.app)
  3. Submit the request and wait a few seconds
  4. You’ll receive 1–2 test AVAX in your wallet

Reminder: These tokens are only usable on Fuji and hold no monetary value.

Step 2: Run a Full Deployment

With your private key and network configuration ready, run your deployment script:

npx hardhat run scripts/deploy.js --network fuji

Take note of the contract address that is printed. You’ll use it to verify interactions and frontend integration.

Step 3: Verify Your Contract on Snowtrace

Verifying your contract allows others to read your source code and interact with it directly on Snowtrace (Avalanche’s equivalent of Etherscan).

Steps:

  1. Go to: https://testnet.snowtrace.io/verifyContract
  2. Paste your contract address
  3. Choose “Solidity (Single file)” and select the same compiler version used in Hardhat
  4. Paste your smart contract code
  5. Submit and wait for verification

Once verified, Snowtrace will show your contract’s public methods and allow test interactions through the browser.

Step 4: Simulate Transactions

Use your Core-connected frontend or a test script to simulate common user actions:

  • Balance Checks: Query balanceOf() for multiple addresses
  • Token Transfers: Send tokens between wallets and check that balances update
  • Invalid Transfers: Try sending more tokens than you own to trigger reverts
  • Frontend Feedback: Ensure the UI updates on transaction confirmation and error states

These tests help you validate both smart contract logic and user experience

Step 5: Watch Logs and Confirmations

When testing, keep an eye on:

  • Transaction hashes and block confirmations
  • Gas usage (watch for unusually high costs)
  • Contract events (use emit statements to debug activity)
  • Core wallet behavior (make sure popups and signatures work as expected)

Tools like Hardhat Console and Snowtrace can help inspect state and debug issues.

Step 6: Collaborate with Testers

If your dApp involves user flows like minting, voting, staking, or bridging, invite other developers or friends to test:

  • Share your frontend and testnet instructions
  • Ask for edge cases: wrong inputs, slow connections, rejected transactions
  • Use Discord or Telegram for real-time feedback

Fuji is meant for breaking things: do it here, not on mainnet.

With successful Fuji tests, you’re almost ready for prime time. You now have:

  • A verified smart contract on a live Avalanche network
  • A frontend connected through Core.app
  • A wallet loaded with test AVAX to simulate real user behavior
  • Confidence that your dApp works end-to-end

Debugging and Testing Your dApp

No matter how simple your smart contract looks, bugs in blockchain apps can be expensive—and permanent. Smart contracts are immutable, so mistakes in production can’t be hotfixed like in Web2. That’s why thorough testing and debugging are non-negotiable.

Here’s how to test and harden your Avalanche dApp before going live.

1. Use Hardhat Console for Live Debugging

Hardhat comes with a powerful built-in console that lets you interact with your contracts in a REPL-like environment. This is ideal for testing contract logic without writing a full script.

npx hardhat console --network fuji

From there, you can run:

const Token = await ethers.getContractAt("MyToken", "0xYourContractAddress");
(await Token.balanceOf("0xYourWallet")).toString()

This gives you fast, interactive feedback for balance checks, function calls, or gas usage—all without deploying a new contract.

2. Write Automated Tests with Mocha and Chai

Hardhat supports Mocha and Chai for writing unit tests. Here’s a sample test for your ERC-20 contract:

Create test/MyToken.test.js:

const { expect } = require("chai");


describe("MyToken", function () {
  let token;
  let owner;
  let addr1;


  beforeEach(async function () {
    const Token = await ethers.getContractFactory("MyToken");
    [owner, addr1] = await ethers.getSigners();
    token = await Token.deploy(ethers.utils.parseEther("1000000"));
    await token.deployed();
  });


  it("Should assign total supply to the owner", async function () {
    const balance = await token.balanceOf(owner.address);
    expect(balance).to.equal(ethers.utils.parseEther("1000000"));
  });


  it("Should transfer tokens correctly", async function () {
    await token.transfer(addr1.address, ethers.utils.parseEther("1000"));
    const balance = await token.balanceOf(addr1.address);
    expect(balance).to.equal(ethers.utils.parseEther("1000"));
  });


  it("Should fail if sender doesn’t have enough tokens", async function () {
    const balanceBefore = await token.balanceOf(owner.address);
    await expect(
      token.connect(addr1).transfer(owner.address, ethers.utils.parseEther("1"))
    ).to.be.revertedWith("ERC20: transfer amount exceeds balance");
    const balanceAfter = await token.balanceOf(owner.address);
    expect(balanceAfter).to.equal(balanceBefore);
  });
});

Run the tests:

npx hardhat test

This gives you confidence your smart contract works correctly across all expected (and unexpected) scenarios.

3. Common Errors and How to Fix Them

Gas Limit Errors If you see out of gas or exceeds block gas limit, try:

  • Reducing complexity of functions
  • Splitting logic into smaller transactions
  • Manually increasing gas in transaction overrides

Revert Messages Use require() statements with clear error messages in Solidity to trace what went wrong.

solidity CopyEdit require(balance >= amount, “Not enough tokens”);

Invalid Opcode / Stack Too Deep Usually caused by overly complex functions or too many local variables. Refactor to smaller units or use structs.

Test Failures Double-check units. Solidity uses wei, so always convert amounts with ethers.utils.parseEther() or formatEther().

4. Best Practices for Smart Contract Security

To make sure you’re fully prepared to deploy on mainnet:

  • Check for overflows/underflows (if not using Solidity 0.8+)
  • Avoid reentrancy: Especially with external calls. Use ReentrancyGuard from OpenZeppelin.
  • Follow the “checks-effects-interactions” pattern
  • Set sensible ownership rules: Who can mint, burn, or pause contracts?
  • Audit when possible: Even basic audits by a peer or open-source contributor are better than none

Remember: On-chain bugs are forever. Catch them before your users do.

5. Simulate High Load or Edge Cases

Use Hardhat scripts to:

  • Simulate hundreds of transactions in a loop
  • Trigger edge-case behaviors (zero balances, large transfers)
  • Deploy multiple instances and simulate contracts talking to each other

This helps ensure your contracts and frontend don’t break under pressure.

When you’re done with all of this, you’ll have:

  • A suite of successful tests
  • A verified contract on Snowtrace
  • A confident sense that your app behaves correctly, securely, and consistently

Deploying to Mainnet

Deploying to Avalanche Mainnet is similar to deploying on Fuji, but with higher stakes. You’re now spending real AVAX and exposing your contract to real users.

Here’s how to do it right.

Step 1: Final Pre-Launch Checklist

Before touching mainnet, make sure:

  • Your smart contracts are fully tested (unit tests + testnet transactions)
  • Contract is verified on Snowtrace (Fuji)
  • Frontend is connected and responsive with Core
  • You’ve reviewed access control (no open admin functions!)
  • Initial values and configurations are correct
  • You have enough AVAX in your wallet for deployment gas

Bonus: Have another developer review your code. A second pair of eyes can spot issues you’ve become blind to.

Step 2: Configure Hardhat for Mainnet

In your hardhat.config.js, add:

js CopyEdit avalanche: { url: “https://api.avax.network/ext/bc/C/rpc”, accounts: [process.env.PRIVATE_KEY] }

Be sure your .env file holds the correct production private key and not your test wallet.

Step 3: Deploy

From the command line:

npx hardhat run scripts/deploy.js --network avalanche

After a few seconds, your contract will be live on Avalanche Mainnet. Take note of the deployed address and transaction hash.

Step 4: Verify on Snowtrace

Once live, verify your contract on Avalanche’s mainnet block explorer:

This adds transparency and enables users/devs to interact with your contract via the explorer.

Step 5: Integrate Mainnet Contract into Frontend

Update your frontend code to:

If you’re using window.ethereum (Core), it will auto-detect the network. Make sure your dApp gracefully handles network mismatches and shows error messages if the user is connected to the wrong chain.

Step 6: Monitor and Maintain

Once live:

  • Monitor transactions on Snowtrace
  • Track errors or exceptions via frontend logging
  • Watch for unusual gas spikes or usage patterns
  • Keep your contract’s admin functions secured or disabled

For upgradability, consider using OpenZeppelin’s proxy pattern—but be aware of the trade-offs and security implications. Immutable contracts are safer, but proxies allow for versioning.

You’ve now:

  • Launched your dApp on Avalanche Mainnet
  • Verified and secured your contracts
  • Deployed with full transparency and user-ready tooling

This is the moment where your side project becomes a real application, open to the world.

Congratulations!

You’ve just walked through every essential step of building, deploying, and scaling a decentralized application on Avalanche. I hope you’ll find Avalanche is the perfect place to grow as a developer.

What sets Avalanche apart isn’t just its speed or low fees. It’s the architecture that was designed for builders. With Avalanche9000, you’re not boxed into someone else’s rules. You define your own chain, your own economics, your own experience.

I hope you’ll take this experience and build on it; make your amazing ideas a reality, and connect with others to help achieve even bigger goals.

© Avalanche 2025