@openzeppelin/contracts-upgradeable
Advanced tools
@openzeppelin/contracts-upgradeable is a library for secure smart contract development. It provides reusable and upgradeable smart contract components that follow best practices in security and gas efficiency. The package is particularly useful for creating upgradeable smart contracts, which can be modified after deployment without changing their address.
Upgradeable Contracts
This feature allows you to create upgradeable contracts using the Initializable base contract. The `initialize` function is used instead of a constructor to set initial values.
```json
{
"code": "import { Initializable } from '@openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol';\n\ncontract MyContract is Initializable {\n uint256 public value;\n\n function initialize(uint256 _value) public initializer {\n value = _value;\n }\n}"}
```Access Control
This feature provides role-based access control mechanisms. The `AccessControlUpgradeable` contract allows you to define roles and restrict access to certain functions based on these roles.
```json
{
"code": "import { AccessControlUpgradeable } from '@openzeppelin/contracts-upgradeable/access/AccessControlUpgradeable.sol';\n\ncontract MyAccessControl is Initializable, AccessControlUpgradeable {\n bytes32 public constant ADMIN_ROLE = keccak256('ADMIN_ROLE');\n\n function initialize(address admin) public initializer {\n _setupRole(ADMIN_ROLE, admin);\n }\n}"}
```ERC20 Token
This feature allows you to create upgradeable ERC20 tokens. The `ERC20Upgradeable` contract provides the standard ERC20 functionality, and the `initialize` function sets the token's name and symbol.
```json
{
"code": "import { ERC20Upgradeable } from '@openzeppelin/contracts-upgradeable/token/ERC20/ERC20Upgradeable.sol';\n\ncontract MyToken is Initializable, ERC20Upgradeable {\n function initialize(string memory name, string memory symbol) public initializer {\n __ERC20_init(name, symbol);\n }\n}"}
```zos-lib is a library for writing upgradeable smart contracts. It provides similar functionalities to @openzeppelin/contracts-upgradeable, including initializable contracts and upgradeable proxies. However, it is less actively maintained compared to @openzeppelin/contracts-upgradeable.
Truffle is a development environment, testing framework, and asset pipeline for Ethereum. While it does not focus solely on upgradeable contracts, it provides tools for managing smart contract development and deployment, including migrations which can be used to handle upgrades.
Hardhat is a development environment for Ethereum software. It offers a flexible and extensible way to manage smart contract development and testing. While it does not provide built-in support for upgradeable contracts, it can be used in conjunction with other libraries like @openzeppelin/contracts-upgradeable to achieve similar functionality.
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.
:building_construction: Want to scale your decentralized application? Check out OpenZeppelin Defender — a mission-critical developer security platform to code, audit, deploy, monitor, and operate with confidence.
[!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.
+> [!NOTE] +> You are looking at the upgradeable variant of OpenZeppelin Contracts. Be sure to review the documentation on Using OpenZeppelin Contracts with Upgrades. +
$ npm install @openzeppelin/contracts-upgradeable
[!WARNING] When installing via git, it is a common error to use the
masterbranch. This is a development branch that should be avoided in favor of tagged releases. The release process involves security measures that themasterbranch does not guarantee.
[!WARNING] Foundry installs the latest version initially, but subsequent
forge updatecommands will use themasterbranch.
$ forge install OpenZeppelin/openzeppelin-contracts-upgradeable
Add @openzeppelin/contracts-upgradeable/=lib/openzeppelin-contracts-upgradeable/contracts/ in remappings.txt.
Once installed, you can use the contracts in the library by importing them:
pragma solidity ^0.8.20;
import {ERC721Upgradeable} from "@openzeppelin/contracts-upgradeable/token/ERC721/ERC721Upgradeable.sol";
contract MyCollectible is ERC721Upgradeable {
function initialize() initializer public {
__ERC721_init("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.
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.
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.
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.
Your use of this Project is governed by the terms found at www.openzeppelin.com/tos (the "Terms").
5.4.0 (2025-07-17)
SignatureChecker, Governor and Governor's extensions. (#5716).Account: Added a simple ERC-4337 account implementation with minimal logic to process user operations. (#5657)AccountERC7579: Extension of Account that implements support for ERC-7579 modules of type executor, validator, and fallback handler. (#5657)AccountERC7579Hooked: Extension of AccountERC7579 that implements support for ERC-7579 hook modules. (#5657)EIP7702Utils: Add a library for checking if an address has an EIP-7702 delegation in place. (#5587)IERC7821, ERC7821: Interface and logic for minimal batch execution. No support for additional opData is included. (#5657)GovernorNoncesKeyed: Extension of Governor that adds support for keyed nonces when voting by sig. (#5574)ERC20Bridgeable: Implementation of ERC-7802 that makes an ERC-20 compatible with crosschain bridges. (#5739)AbstractSigner, SignerECDSA, SignerP256, and SignerRSA: Add an abstract contract and various implementations for contracts that deal with signature verification. (#5657)SignerERC7702: Implementation of AbstractSigner for Externally Owned Accounts (EOAs). Useful with ERC-7702. (#5657)SignerERC7913: Abstract signer that verifies signatures using the ERC-7913 workflow. (#5659)MultiSignerERC7913: Implementation of AbstractSigner that supports multiple ERC-7913 signers with a threshold-based signature verification system. (#5659)MultiSignerERC7913Weighted: Extension of MultiSignerERC7913 that supports assigning different weights to each signer, enabling more flexible governance schemes. (#5741)ERC7913P256Verifier and ERC7913RSAVerifier: Ready to use ERC-7913 verifiers that implement key verification for P256 (secp256r1) and RSA keys. (#5659)SignatureChecker: Add support for ERC-7913 signatures alongside existing ECDSA and ERC-1271 signature verification. (#5659)ERC7739: An abstract contract to validate signatures following the rehashing scheme from ERC7739Utils. (#5664)ERC7739Utils: Add a library that implements a defensive rehashing mechanism to prevent replayability of smart contract signatures based on the ERC-7739. (#5664)EnumerableMap: Add support for BytesToBytesMap type. (#5658)EnumerableMap: Add keys(uint256,uint256) that returns a subset (slice) of the keys in the map. (#5713)EnumerableSet: Add support for StringSet and BytesSet types. (#5658)EnumerableSet: Add values(uint256,uint256) that returns a subset (slice) of the values in the set. (#5713)Arrays: Add unsafeAccess, unsafeMemoryAccess and unsafeSetLength for bytes[] and string[]. (#5568)Blockhash: Add a library that provides access to historical block hashes using EIP-2935's history storage, extending the standard 256-block limit to 8191 blocks. (#5642)Bytes: Fix lastIndexOf(bytes,byte,uint256) with empty buffers and finite position to correctly return type(uint256).max instead of accessing uninitialized memory sections. (#5797)FAQs
Secure Smart Contract library for Solidity
The npm package @openzeppelin/contracts-upgradeable receives a total of 183,151 weekly downloads. As such, @openzeppelin/contracts-upgradeable popularity was classified as popular.
We found that @openzeppelin/contracts-upgradeable demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 6 open source maintainers collaborating on the project.
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