openzeppelin-contracts README

The project's README from github.com/OpenZeppelin/openzeppelin-contracts. As one markdown file: README.md.

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A library for secure smart contract development. Build on a solid foundation of community-vetted code.

:mage: Not sure how to get started? Check out Contracts Wizard — an interactive smart contract generator.

[!IMPORTANT] OpenZeppelin Contracts uses semantic versioning to communicate backwards compatibility of its API and storage layout. For upgradeable contracts, the storage layout of different major versions should be assumed incompatible, for example, it is unsafe to upgrade from 4.9.3 to 5.0.0. Learn more at Backwards Compatibility.

Overview

Release tags

We use NPM tags to clearly distinguish between audited and non-audited versions of our package:

Tag Purpose Description
latest ✅ Audited releases Stable, audited versions of the package. This is the default version installed when users run npm install @openzeppelin/contracts.
dev 🧪 Final but not audited Versions that are finalized and feature-complete but have not yet been audited. This version is fully tested, can be used in production and is covered by the bug bounty.
next 🚧 Release candidates Pre-release versions that are not final. Used for testing and validation before the version becomes a final dev or latest release.

Installation

Hardhat (npm)

$ npm install @openzeppelin/contracts

→ Installs the latest audited release (latest).

$ npm install @openzeppelin/contracts@dev

→ Installs the latest unaudited release (dev).

Foundry (git)

[!WARNING] When installing via git, it is a common error to use the master branch. This is a development branch that should be avoided in favor of tagged releases. The release process involves security measures that the master branch does not guarantee.

[!WARNING] Foundry installs the latest version initially, but subsequent forge update commands will use the master branch.

$ forge install OpenZeppelin/openzeppelin-contracts

Add @openzeppelin/contracts/=lib/openzeppelin-contracts/contracts/ in remappings.txt.

Usage

Once installed, you can use the contracts in the library by importing them:

pragma solidity ^0.8.20;

import {ERC721} from "@openzeppelin/contracts/token/ERC721/ERC721.sol";

contract MyCollectible is ERC721 {
    constructor() ERC721("MyCollectible", "MCO") {
    }
}

If you're new to smart contract development, head to Developing Smart Contracts to learn about creating a new project and compiling your contracts.

To keep your system secure, you should always use the installed code as-is, and neither copy-paste it from online sources nor modify it yourself. The library is designed so that only the contracts and functions you use are deployed, so you don't need to worry about it needlessly increasing gas costs.

Learn More

The guides in the documentation site will teach about different concepts, and how to use the related contracts that OpenZeppelin Contracts provides:

The full API is also thoroughly documented, and serves as a great reference when developing your smart contract application. You can also ask for help or follow Contracts' development in the community forum.

Finally, you may want to take a look at the guides on our blog, which cover several common use cases and good practices. The following articles provide great background reading, though please note that some of the referenced tools have changed, as the tooling in the ecosystem continues to rapidly evolve.

Security

This project is maintained by OpenZeppelin with the goal of providing a secure and reliable library of smart contract components for the ecosystem. We address security through risk management in various areas such as engineering and open source best practices, scoping and API design, multi-layered review processes, and incident response preparedness.

The OpenZeppelin Contracts Security Center contains more details about the secure development process.

The security policy is detailed in SECURITY.md as well, and specifies how you can report security vulnerabilities, which versions will receive security patches, and how to stay informed about them. We run a bug bounty program on Immunefi to reward the responsible disclosure of vulnerabilities.

The engineering guidelines we follow to promote project quality can be found in GUIDELINES.md.

Past audits can be found in audits/.

Smart contracts are a nascent technology and carry a high level of technical risk and uncertainty. Although OpenZeppelin is well known for its security audits, using OpenZeppelin Contracts is not a substitute for a security audit.

OpenZeppelin Contracts is made available under the MIT License, which disclaims all warranties in relation to the project and which limits the liability of those that contribute and maintain the project, including OpenZeppelin. As set out further in the Terms, you acknowledge that you are solely responsible for any use of OpenZeppelin Contracts and you assume all risks associated with any such use.

Contribute

OpenZeppelin Contracts 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 Contracts is released under the MIT License.

Your use of this Project is governed by the terms found at www.openzeppelin.com/tos (the "Terms").

openzeppelin-contracts (OpenZeppelin/openzeppelin-contracts)

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27.3K ·GitHub
Openzeppelin-contracts
What is this?A library for secure smart contract development on Ethereum: community-vetted Solidity code with implementations of standards like ERC-20 and ERC-721, plus a flexible role-based permissioning scheme.
Is it a framework I build my project on, or a library I import into my contracts?It's a Solidity library: you import the contracts you need into your own code, and only the contracts and functions you use get deployed on-chain.
How do I add it to my Hardhat or Foundry project?For Hardhat, npm install @openzeppelin/contracts fetches the audited release. For Foundry, install via git and add @openzeppelin/contracts/=lib/openzeppelin-contracts/contracts/ to remappings.txt — stick to tagged releases, not the master branch.
If my contracts use OpenZeppelin, are they automatically secure?No — the README is explicit that using OpenZeppelin Contracts is not a substitute for a security audit, and smart contracts carry a high level of technical risk.
Can I use it in commercial projects?Yes — it's released under the MIT License, though it disclaims all warranties and you're solely responsible for any use and its risks.
What's inside the library?Token implementations for ERC-20, ERC-721, ERC-1155 and ERC-6909, role-based access control, and utilities like non-overflowing math, signature verification and trustless paying systems.
Will importing the whole library inflate my gas costs?No. Only the contracts and functions you actually use are deployed, so the library is designed not to needlessly increase gas costs.
What is Contracts Wizard?An interactive smart contract generator from OpenZeppelin; the README points newcomers there when they're not sure how to get started.
Can I upgrade a deployed upgradeable contract to a new major version?Storage layouts of different major versions should be assumed incompatible — the README flags upgrading for example from 4.9.3 to 5.0.0 as unsafe.
What are similar projects?union, hashsigs-solidity, shardeum, go-ethereum, solidity, ethereum-sdk, foundry, DeFiBridgeDiamond
Which topics is it in?evm, solidity, ethereum, smart-contracts, decentralized, cryptocurrency, web3, blockchain, security, npm, library, developer-tools
Creator
OpenZeppelin
Size
52.1 MB
Stars
27.3K
Updated
CommitOct 16Releasev5.7.0Jul 29
Age
10y
Commits · 90 Days