_Follow along the course with this video._ --- ### ERC20 OpenZeppelin Welcome back! As mentioned in the closing of our last lesson, we could absolutely continue with manually building out a smart contract comprised of all the required functions to be compatible with the ERC20 standard, but wouldn't it be more convenient to use pre-deployed, audited, and ready-to-go contracts? In this section, I'll guide you on using the OpenZeppelin Library to achieve this. > ❗ **NOTE** > OpenZeppelin is renowned for its Smart Contract framework, offering a vast repository of audited contracts readily integrable into your codebase. Access [OpenZeppelin's documentation](https://docs.openzeppelin.com/contracts/5.x/) via their official website. By navigating to [Products -> Contracts Library](https://www.openzeppelin.com/contracts), you can discover a vast array of ready-to-use contracts. Additionally, OpenZeppelin offers a contract wizard, streamlining the contract creation process — perfect for tokens, governances, or custom contracts. ::image{src='/foundry-erc20s/3-erc20-open-zeppelin/erc20-open-zeppelin1.PNG' style='width: 100%; height: auto;'} Let's leverage OpenZeppelin to create a new ERC20 Token. Create a new file within `src` named `OurToken.sol`. Once that's done, let's install the OpenZeppelin library into our contract. ```bash forge install OpenZeppelin/openzeppelin-contracts --no-commit ``` Once installed you'll see the ERC20 contract from OpenZeppelin within `lib/openzeppelin-contracts/token/ERC20/ERC20.sol`. Let's add a remapping in our foundry.toml to make importing a little easier on us.Within foundry.toml add the line: ```toml remappings = ["@openzeppelin=lib/openzeppelin-contracts"] ``` We can now import and inherit this contract into `OurToken.sol`! ```solidity // SPDX-License-Identifier: MIT pragma solidity ^0.8.18; import "@openzeppelin/contracts/token/ERC20/ERC20.sol"; contract OurToken is ERC20 { //constructor goes here } ``` By importing the OpenZeppelin implementation of ERC20 this way, we inherit all the functionality of the ERC20 standard with much less work and a level of confidence that the code has been testing and verified. > ❗ **PROTIP** > If you're looking for an alternative library full of trusted contracts, I recommend looking at the [**Solmate Repo**](https://github.com/transmissions11/solmate) by Transmissions11. Now, we should recall that when inheriting from a contract with a constructor, our contract must fulfill the requirements of that constructor. We'll need to define details like a name and symbol for OurToken. ```solidity // SPDX-License-Identifier: MIT pragma solidity ^0.8.18; import "@openzeppelin/contracts/token/ERC20/ERC20.sol"; contract OurToken is ERC20 { constructor(uint256 initialSupply) ERC20("OurToken", "OT") { _mint(msg.sender, initialSupply); } } ``` For the purposes of simple examples like this, I like to mint the initialSupply to the deployer/msg.sender, which I've demonstrated above. As always we can perform a sanity check to assure things are working as expected by running `forge build`. ::image{src='/foundry-erc20s/3-erc20-open-zeppelin/erc20-open-zeppelin2.PNG' style='width: 100%; height: auto;'} Nailed it. See you in the next lesson where we'll look into how to deploy this bad Larry.