@openzeppelin/contracts

What is @openzeppelin/contracts?

@openzeppelin/contracts is a library for secure smart contract development. It provides implementations of standards like ERC20 and ERC721, as well as utilities for common tasks such as access control and upgradeability.

What are @openzeppelin/contracts's main functionalities?

ERC20 Token

This code demonstrates how to create an ERC20 token using the @openzeppelin/contracts library. The ERC20 contract is imported and extended to create a new token with an initial supply.

const { ERC20 } = require('@openzeppelin/contracts/token/ERC20/ERC20.sol');

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

ERC721 Token

This code demonstrates how to create an ERC721 non-fungible token (NFT) using the @openzeppelin/contracts library. The ERC721 contract is imported and extended to create a new NFT with a minting function.

const { ERC721 } = require('@openzeppelin/contracts/token/ERC721/ERC721.sol');

contract MyNFT is ERC721 {
    constructor() ERC721("MyNFT", "MNFT") {
    }

    function mint(address to, uint256 tokenId) public {
        _mint(to, tokenId);
    }
}

Access Control

This code demonstrates how to use the Ownable contract from the @openzeppelin/contracts library to restrict access to certain functions. The onlyOwner modifier ensures that only the contract owner can call the restrictedFunction.

const { Ownable } = require('@openzeppelin/contracts/access/Ownable.sol');

contract MyContract is Ownable {
    function restrictedFunction() public onlyOwner {
        // restricted logic
    }
}

Upgradeability

This code demonstrates how to use the TransparentUpgradeableProxy contract from the @openzeppelin/contracts library to create upgradeable smart contracts. The proxy pattern allows for the logic of the contract to be upgraded while preserving the contract's state.

const { TransparentUpgradeableProxy } = require('@openzeppelin/contracts/proxy/transparent/TransparentUpgradeableProxy.sol');

contract MyContractV1 {
    uint256 public value;

    function setValue(uint256 _value) public {
        value = _value;
    }
}

contract MyContractV2 {
    uint256 public value;

    function setValue(uint256 _value) public {
        value = _value * 2;
    }
}

Other packages similar to @openzeppelin/contracts

solidity-rlp

solidity-rlp is a library for encoding and decoding RLP (Recursive Length Prefix) data in Solidity. While it focuses on a specific encoding format, @openzeppelin/contracts provides a broader range of utilities and standard implementations for smart contract development.

truffle

Truffle is a development environment, testing framework, and asset pipeline for Ethereum. While Truffle provides tools for developing and testing smart contracts, @openzeppelin/contracts offers a library of secure and reusable smart contract components.

hardhat

Hardhat is a development environment to compile, deploy, test, and debug Ethereum software. Similar to Truffle, it focuses on the development workflow, whereas @openzeppelin/contracts provides pre-built smart contract components.

README

OpenZeppelin Contracts is a library for secure smart contract development. It provides implementations of standards like ERC20 and ERC721 which you can deploy as-is or extend to suit your needs, as well as Solidity components to build custom contracts and more complex decentralized systems.

Install

npm install @openzeppelin/contracts

OpenZeppelin Contracts features a stable API, which means your contracts won't break unexpectedly when upgrading to a newer minor version. You can read ṫhe details in our API Stability document.

Usage

To write your custom contracts, import ours and extend them through inheritance.

pragma solidity ^0.5.0;

import "@openzeppelin/contracts/token/ERC721/ERC721Full.sol";
import "@openzeppelin/contracts/token/ERC721/ERC721Mintable.sol";

contract MyNFT is ERC721Full, ERC721Mintable {
  constructor() ERC721Full("MyNFT", "MNFT") public {
  }
}

You need an ethereum development framework for the above import statements to work! Check out these guides for Truffle, Embark or Buidler.

On our site you will find a few guides to learn about the different parts of OpenZeppelin, as well as documentation for the API. Keep in mind that the API docs are work in progress, and don’t hesitate to ask questions in our forum.

Security

This project is maintained by OpenZeppelin, and developed following our high standards for code quality and security. OpenZeppelin is meant to provide tested and community-audited code, but please use common sense when doing anything that deals with real money! We take no responsibility for your implementation decisions and any security problems you might experience.

The core development principles and strategies that OpenZeppelin is based on include: security in depth, simple and modular code, clarity-driven naming conventions, comprehensive unit testing, pre-and-post-condition sanity checks, code consistency, and regular audits.

The latest audit was done on October 2018 on version 2.0.0.

Please report any security issues you find to [e-mail].

Contribute

OpenZeppelin exists thanks to its contributors. There are many ways you can participate and help build high quality software. Check out the contribution guide!

License

OpenZeppelin is released under the MIT License.