mirror of openzeppelin-contracts
You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
Francisco 8f8fd84f1e
Improve some NatSpec and revert reasons (#3809)
17 hours ago
.github Update crytic/slither-action action to v0.2.0 (#3751) 2 months ago
audit Fix many spelling errors (#3274) 8 months ago
certora Set up codespell (#3643) 3 months ago
contracts Improve some NatSpec and revert reasons (#3809) 17 hours ago
docs Fix whitespace in docs (#3832) 3 days ago
hardhat Ignore specific warnings and make the rest into errors (#3695) 2 months ago
lib Add ERC4626 standard property tests (#3792) 3 weeks ago
scripts Improve some NatSpec and revert reasons (#3809) 17 hours ago
test Improve some NatSpec and revert reasons (#3809) 17 hours ago
.codecov.yml Remove Codecov Patch status outside PRs 3 months ago
.editorconfig Remove line length configuration for markdown files 4 months ago
.eslintrc Report changes to contract construction cost in CI (#3579) 4 months ago
.gitattributes feat: add solidity syntax highlighting directive, fixes #671 5 years ago
.gitignore Add Certora's Governance verification rules (#2997) 11 months ago
.gitmodules Add ERC4626 standard property tests (#3792) 3 weeks ago
.mocharc.js Use Hardhat recommended Mocha configuration (#2805) 1 year ago
.prettierrc Add AddressToUintMap (#3150) 10 months ago
.solcover.js Update lockfile (#2412) 2 years ago
.solhint.json remove duplicated 'private-vars-leading-underscore' solhint rule (#2800) 1 year ago
CHANGELOG.md Merge branch 'release-v4.8' 2 weeks ago
CODE_OF_CONDUCT.md Create CODE_OF_CONDUCT.md (#1061) 4 years ago
CONTRIBUTING.md Fix minor typo in CONTRIBUTING.md. (#3284) 8 months ago
DOCUMENTATION.md Fix typos (#2343) 2 years ago
GUIDELINES.md Use "OpenZeppelin Contracts" where appropriate (#2778) 1 year ago
LICENSE Update Copyright notice and include contributors 10 months ago
README.md Improve readme style (#3577) 4 months ago
RELEASING.md Use "OpenZeppelin Contracts" where appropriate (#2778) 1 year ago
SECURITY.md Update security email domain and Immunefi text 1 year ago
foundry.toml Add ERC4626 standard property tests (#3792) 3 weeks ago
hardhat.config.js Update docs pipeline to solidity-docgen@0.6 (#3707) 2 months ago
logo.svg use svg logo for better scaling 2 years ago
netlify.toml Fix documentation previews in pull requests (#2015) 3 years ago
package-lock.json Update lockfile 2 weeks ago
package.json Merge branch 'release-v4.8' 2 weeks ago
renovate.json configure renovate using openzeppelin shareable config 2 years ago
slither.config.json Use slither action (#3278) 8 months ago



Docs NPM Package Coverage Status gitpoap badge

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

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

🏗 Want to scale your decentralized application? Check out OpenZeppelin Defender — a secure platform for automating and monitoring your operations.



$ npm install @openzeppelin/contracts

OpenZeppelin Contracts features a stable API, which means that your contracts won't break unexpectedly when upgrading to a newer minor version.

An alternative to npm is to use the GitHub repository (openzeppelin/openzeppelin-contracts) to retrieve the contracts. When doing this, make sure to specify the tag for a release such as v4.5.0, instead of using the master branch.


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

pragma solidity ^0.8.0;

import "@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:

  • Access Control: decide who can perform each of the actions on your system.
  • Tokens: create tradeable assets or collectives, and distribute them via Crowdsales.
  • Gas Station Network: let your users interact with your contracts without having to pay for gas themselves.
  • Utilities: generic useful tools including non-overflowing math, signature verification, and trustless paying systems.

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's 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.


This project is maintained by OpenZeppelin, and developed following our high standards for code quality and security. OpenZeppelin Contracts 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 Contracts 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.

We have a bug bounty program on Immunefi. Please report any security issues you find through the Immunefi dashboard, or reach out to security@openzeppelin.com.

Critical bug fixes will be backported to past major releases.


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!


OpenZeppelin Contracts is released under the MIT License.