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

• Implementations of standards likeERC20 andERC721.
• Flexiblerole-based permissioning scheme.
• ReusableSolidity components to build custom contracts and complex decentralized systems.

🧙Not sure how to get started? Check outContracts Wizard — an interactive smart contract generator.

🏗️Want to scale your decentralized application? Check outOpenZeppelin Defender — a mission-critical developer security platform to code, audit, deploy, monitor, and operate with confidence.

$ npm install @openzeppelin/contracts

$ forge install OpenZeppelin/openzeppelin-contracts

Add@openzeppelin/contracts/=lib/openzeppelin-contracts/contracts/ inremappings.txt.

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";contractMyCollectibleisERC721 {constructor()ERC721("MyCollectible","MCO") {    }}

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

To keep your system secure, you shouldalways 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.

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

• Access Control: decide who can perform each of the actions on your system.
• Tokens: create tradeable assets or collectives, and distribute them viaCrowdsales.
• Utilities: generic useful tools including non-overflowing math, signature verification, and trustless paying systems.

Thefull 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 thecommunity forum.

Finally, you may want to take a look at theguides 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.

• The Hitchhiker’s Guide to Smart Contracts in Ethereum will help you get an overview of the various tools available for smart contract development, and help you set up your environment.
• A Gentle Introduction to Ethereum Programming, Part 1 provides very useful information on an introductory level, including many basic concepts from the Ethereum platform.
• For a more in-depth dive, you may read the guideDesigning the Architecture for Your Ethereum Application, which discusses how to better structure your application and its relationship to the real world.

This project is maintained byOpenZeppelin 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.

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

The security policy is detailed inSECURITY.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 abug bounty program on Immunefi to reward the responsible disclosure of vulnerabilities.

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

Past audits can be found inaudits/.

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.

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

OpenZeppelin Contracts is released under theMIT License.

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