@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 secure platform for automating and monitoring your operations.
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
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-upgradeable) 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-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'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 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 security policy is detailed in SECURITY.md, 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").
4.9.3 (2023-07-28)
ERC2771Context: Return the forwarder address whenever the msg.data of a call originating from a trusted forwarder is not long enough to contain the request signer address (i.e. msg.data.length is less than 20 bytes), as specified by ERC-2771. (#4481)ERC2771Context: Prevent revert in _msgData() when a call originating from a trusted forwarder is not long enough to contain the request signer address (i.e. msg.data.length is less than 20 bytes). Return the full calldata in that case. (#4484)FAQs
Secure Smart Contract library for Solidity
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 4 open source maintainers collaborating on the project.
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