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 Giordano 21c5d623d6 Update Copyright notice and include contributors 2 years ago
.github Add workflow to generate and update docs branches 2 years ago
audit Use "OpenZeppelin Contracts" where appropriate (#2778) 2 years ago
certora Add Certora's Governance verification rules (#2997) 2 years ago
contracts Add test and docs describing a misuse of MerkleProof (#3090) 2 years ago
docs Fix use of ^ (xor) instead of ** (power) (#3130) 2 years ago
hardhat Transition from buidler to hardhat 3 years ago
migrations Clean up npm package (#904) 6 years ago
scripts Lint 2 years ago
test Add test and docs describing a misuse of MerkleProof (#3090) 2 years ago
.codecov.yml Configure Codecov parameters 3 years ago
.editorconfig Add documentation for proxies (#2344) 3 years ago
.eslintrc Migrate to Hardhat (#2397) 3 years ago
.gitattributes feat: add solidity syntax highlighting directive, fixes #671 6 years ago
.gitignore Add Certora's Governance verification rules (#2997) 2 years ago
.mocharc.js Use Hardhat recommended Mocha configuration (#2805) 2 years ago
.prettierrc Add Prettier for linting and fix Solhint config (#2697) 3 years ago
.solcover.js Update lockfile (#2412) 3 years ago
.solhint.json remove duplicated 'private-vars-leading-underscore' solhint rule (#2800) 2 years ago
CHANGELOG.md Fix typo in CHANGELOG (#3138) 2 years ago
CODE_OF_CONDUCT.md Create CODE_OF_CONDUCT.md (#1061) 6 years ago
CONTRIBUTING.md Use "OpenZeppelin Contracts" where appropriate (#2778) 2 years ago
DOCUMENTATION.md Fix typos (#2343) 3 years ago
GUIDELINES.md Use "OpenZeppelin Contracts" where appropriate (#2778) 2 years ago
LICENSE Update Copyright notice and include contributors 2 years ago
README.md Update security email domain and Immunefi text 2 years ago
RELEASING.md Use "OpenZeppelin Contracts" where appropriate (#2778) 2 years ago
SECURITY.md Update security email domain and Immunefi text 2 years ago
hardhat.config.js Re-enable immutable forwarder in ERC2771Context (#2917) 2 years ago
logo.svg use svg logo for better scaling 3 years ago
netlify.toml Fix documentation previews in pull requests (#2015) 4 years ago
package-lock.json upgrade solidity-coverage to 0.7.18 to support ERC165 coverage (#3117) 2 years ago
package.json Add Slither reentrancy check in CI (#3047) 2 years ago
renovate.json configure renovate using openzeppelin shareable config 3 years ago



Docs NPM Package Coverage Status

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.



$ 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.


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 docs 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, 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.