OpenZeppelin is a company that offer free and open source framework for creating smart contracts.

(They also offer other services, such as smart contract audits).

Their smart contracts cover many ERC standard interfaces. As of the type of writing the current version of their contracts is v4.

You can find them on https://docs.openzeppelin.com/contracts/4.x/

Some of the most common OpenZeppelin smart contracts are:

• ERC20 https://docs.openzeppelin.com/contracts/4.x/erc20
• ERC721 https://docs.openzeppelin.com/contracts/4.x/erc721
• Permission/access control https://docs.openzeppelin.com/contracts/4.x/access-control

You can install them with:

npm install @openzeppelin/contracts

and then use them in your smart contracts like this:

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC721/ERC721.sol";

contract YourNFT is ERC721 {
    constructor() ERC721("YourNFT", "YNFT") {
    }
}

There are lots of Solidity utilities you can import in such as:

• Base64 https://docs.openzeppelin.com/contracts/4.x/api/utils#Base64
• Counters https://docs.openzeppelin.com/contracts/4.x/api/utils#Counters

Spotted a typo or have a suggestion to make this crypto dev article better? Please let me know!