Smart Contract Development - OpenZeppelin Contracts 5.0 Overview

October 13, 2023
Smart Contract Development - OpenZeppelin Contracts 5.0 Overview

In the ever-evolving landscape of blockchain and decentralized applications, staying at the forefront of security and efficiency is paramount. Smart contract developers and smart contract development companies are continuously on the lookout for tools and libraries that can help them create robust, reliable, and future-proof solutions. OpenZeppelin, a renowned leader in blockchain security, has recently unveiled a groundbreaking update that is set to reshape the way we approach smart contract development.

OpenZeppelin, established in 2015, is a global leader in fortifying blockchain applications and smart contracts. Their open-source Contract Libraries are the industry standard, offering security and reliability to smart contract development. With the Defender developer security platform, OpenZeppelin's expertise guides project teams through the entire development life cycle, ensuring faster and safer planning, coding, auditing, deployment, and operation.

OpenZeppelin Contracts 5.0 is a pivotal release, marking the first major update to the Solidity library since 2021. This latest iteration reflects the commitment of the OpenZeppelin team to upgrade their library, enhance efficiency, and adhere to state-of-the-art security practices. For smart contract developers and development companies, this means gaining access to a refreshed suite of tools and features designed to simplify, secure, and optimize their development process.

The Unwavering Commitment to Blockchain Developers

OpenZeppelin Contracts, already the most widely adopted Solidity library for Ethereum and other EVM blockchains, have equipped developers with the essential tools needed to craft secure, efficient, and future-proof smart contract systems. With the release of OpenZeppelin Contracts 5.0, this commitment to empowering developers is more robust than ever before.

What's New in OpenZeppelin Contracts 5.0

  1. Modern Best Practices Out-of-the-Box

The new version incorporates modern best practices, making it easier for smart contract developers to follow industry standards and build secure contracts. One notable addition is "namespaced storage," simplifying data management and reducing the likelihood of bugs.

  1. Simplified Codebase for Enhanced Security

In the pursuit of heightened security, OpenZeppelin has streamlined its codebase. Fewer lines of code mean fewer potential vulnerabilities. This change simplifies the auditing process and underscores the company's dedication to making secure smart contract development accessible.

  1. Efficiency Improvements

OZ Contracts 5.0 are designed to be more gas-efficient. Lower gas consumption translates to more cost-effective transactions and more accessible applications for users. This is especially important for projects seeking widespread adoption and cost-effectiveness.

  1. Modernising Access Control with AccessManager

Access control is crucial for the security of smart contracts. OpenZeppelin Contracts 5.0 introduces AccessManager, a tool that streamlines access control, making it easier for developers to manage who can interact with their smart contracts. This not only enhances security but also simplifies the development process.

  1. Advanced Testing

The release includes an array of advanced testing features, including new fuzzing and formal verification rules. These testing capabilities are vital for ensuring that smart contracts behave as expected under various conditions, and they represent a significant step forward in making smart contracts more reliable.

OpenZeppelin Contracts 5.0 is a game-changer for smart contract developers and blockchain development companies alike. With a renewed focus on security, efficiency, and user-friendly features, OpenZeppelin has set a new standard for building secure and reliable smart contract systems. This update empowers developers to create blockchain solutions that not only meet current standards but are also future-proofed against emerging challenges.

Smart Contracts Development - Unveiling Modernised Contracts 5.0

The landscape of smart contracts development has undergone a significant transformation since our previous major release, Contracts 4.0. This evolution includes improvements in compiler features and the integration of contemporary standardized practices. Contracts 5.0 introduces a modernized array of features aimed at enhancing security, efficiency, and the overall developer experience in the realm of smart contracts development.


In OZ Contracts 5.0, significant simplifications have been introduced to enhance the efficiency and security of smart contract development. Notable changes include the removal of token hooks from ERC20, ERC721, and ERC1155, which have been replaced with a single’ _update’ function. This function can be overridden by developers to accommodate custom behaviors in operations such as mint, transfer, or burn.

Smart Contract development: Open Zeppelin Contracts v4 Vs Contracts v5

Source: OpenZeppelin

Additionally, Ownable now offers the flexibility to include a custom owner argument during contract construction. As for the Governor, it now supports voting through bytes-formatted signatures and implements Account Abstraction, aligning with the ERC-1271 standard.

To optimize efficiency and fortify security, certain functions and contracts have been removed in this release. It's worth noting that some of these may potentially return in future versions with enhanced support.

Key removals in OpenZeppelin Contracts 5.0 include:

  • Address.isContract
  • Counters
  • SafeMath
  • SignedSafeMath
  • GovernorCompatibilityBravo
  • GovernorVotesComp
  • TokenTimelock (replaced by VestingWallet)
  • ERC777
  • All cross-chain contracts (including AccessControlCrossChain)
  • All presets have been replaced in favor of the OpenZeppelin Contracts Wizard.

These simplifications and streamlining measures in OpenZeppelin Contracts 5.0 are designed to cultivate a more efficient and secure environment for smart contract development, ensuring a smoother experience for developers in this rapidly evolving field.

Implementing Namespaced Storage for Enhanced Security in Upgrades

In the pursuit of bolstering security and alleviating the challenges associated with storage layout changes in complex upgradeable contracts, OZ 5.0 proposes an approach to implementing ERC-7201: Namespaced Storage Layout.

This innovative approach draws inspiration from the diamond storage pattern while standardizing it in a manner that facilitates safety checks through OZ tooling, all while mitigating potential security risks. This Namespaced Storage pattern is seamlessly integrated into the new version to address one of the most prevalent and often overlooked security issues in the realm of upgrades: storage layout collisions between different implementation versions.

Previously, upgradeable contracts employed a ’ __gap’  variable in storage, strategically placed between inherited contracts to reserve space for accommodating new variables introduced during upgrades. However, in this latest version, storage locations are expertly namespaced using ERC-7201. This strategic move allows for the addition of variables without compromising previously stored data.

By segregating variables into specific namespaces, each inherited contract retains its distinct storage pointer, providing the flexibility to accommodate more values with each subsequent upgrade. This innovative approach not only streamlines the upgrade process but also enhances the overall security of the smart contract, ensuring that developers can confidently make necessary improvements without jeopardizing the existing data.

Harnessing the Power of New Solidity Compiler Features

OpenZeppelin Contracts has taken a significant step forward by updating to Solidity 0.8.20, leveraging the latest enhancements in the Solidity language. This update introduces a range of new features that enhance the efficiency and development experience within the smart contract ecosystem.

Custom Errors and Explicit Imports

With this update, OpenZeppelin Contracts now supports custom errors, a feature previously absent but now following standard practices for error construction. Historically, applications relied on plain strings within reverts (e.g., revert("Unauthorized")) to convey error information.

Smart Contract Development: OpenZeppelin Contracts v5.0 Custom Errors

Source: OpenZeppelin

However, this new addition is inspired by community feedback and the ERC-6093 specification. Custom errors offer developers a more efficient and standardized method of reporting errors in their smart contracts. What's more, these errors can include dynamic arguments, offering greater flexibility in error handling.

Another noteworthy addition in OpenZeppelin Contracts 5.0 is the introduction of explicit imports. This feature aims to streamline the development process by avoiding clutter in the global scope and simplifying the developer's ability to track import paths. These explicit imports contribute to code clarity and ease of understanding.

Tooling Updates for Smart Contract Development

Upgrades Plugins and OpenZeppelin Contracts Wizard:

Along with the core library updates, OZ 5.0 includes enhancements to Upgrades Plugins and OpenZeppelin Contracts Wizard. This ensures that developers can access the most comprehensive and efficient toolset for their smart contract developmentendeavors. Notably, our ongoing commitment to support Hardhat is reinforced, and OZ is planning to add upgrade support for Foundry later this year.

Integration with OpenZeppelin Defender:

A significant development in this release is the native integration of the Contracts library with the OpenZeppelin Defender security platform. This integration expands open-source contract standards by offering enhanced security, performance, and support features to empower smart contract developers:

  • Secure Code: Maximizing the security of your code and ensuring that dependencies are up to date is paramount. OpenZeppelin Defender provides tools to help you maintain secure and up-to-date code.
  • Secure Deploy: Deploying smart contracts is now accompanied by automatic checks on your storage layout to prevent upgrade collisions. This feature adds an extra layer of security and confidence to your deployments.
  • Monitor, Respond, and Operate: With built-in templates for implemented standards, you can now monitor your live applications efficiently. Additionally, instant response mechanisms are in place to address potential threats swiftly, ensuring the stability and security of your smart contracts.

These tooling updates are designed to make smart contract development more robust, secure, and user-friendly. They provide developers with a comprehensive set of features to streamline the development process and ensure that their smart contracts meet the highest standards of security, performance, and compliance in the ever-evolving world of smart contract development.

Optimizing Gas Efficiency While Upholding Security

Through a series of extensive optimizations throughout the library, OZ has effectively reduced both deployment and runtime costs. These optimizations strike a balance between code readability and efficiency. Notably, these gas cost reductions have resulted in an impressive 9.63% average reduction in the top 10 optimized methods. Furthermore, deployment costs have seen a substantial average cutback of 27.11% among the top 10 reduced contracts.

Replacing Revert Strings with Custom Errors

An innovative change in the update is the introduction of custom errors to the library. This approach has yielded a 12.84% average drop in deployment costs across the entire library.  The key driver behind these reductions in deployment costs lies in the removal of revert strings from the bytecode size. The revert strings, no longer stored within the contract bytecode, were responsible for over 20% of deployment costs in contracts with extensive usage of lengthy revert strings, such as those associated with AccessControl.

Reducing Duplicate SLOADs and Leveraging Immutable Variables:

Storage reads are known to be among the most resource-intensive operations during runtime. OZ Contracts 5.0 takes a significant step in gas optimization by avoiding duplicate SLOADs

Moreover, the library now incorporates a greater number of immutable variables, effectively mitigating unnecessary storage reads. This efficient approach is exemplified in various instances, such as TransparentUpgradeableProxy and BeaconProxy, where key parameters, like admin or beacon, are stored as immutable variables. This smart choice results in reduced reads during every interaction with these proxies, significantly optimizing the performance.

Packing Variables for Reduced Storage Consumption

OpenZeppelin Contracts 5.0 undertakes a meticulous reorganization of frequently used data structures and variables to minimize storage usage. The aim is to cut down on the gas costs associated with both reading and writing such variables.

A case in point is the updated Governor proposal structure, which previously consumed 3 storage slots and included multiple storage gaps for backward compatibility. The new structure is ingeniously designed to occupy just 2 slots, with variables commonly used together sharing the same slot. This approach not only reduces unnecessary storage reads but also enhances gas consumption efficiency, resulting in significant cost savings.

By minimizing storage-related overhead and improving gas consumption, these enhancements provide substantial benefits to developers in the ever-evolving field of smart contract development.

Flexible and Transparent Access Management for Smart Contract Development

As the smart contract development industry continues to evolve, systems are growing in complexity, particularly in the realm of permissions and role management. These intricate systems often involve multiple contracts, coordinated through various mechanisms like multisigs, DAOs, timelocks, and externally owned accounts (EOAs).

This complexity has stretched the capabilities of previous access management tools like AccessControl and Ownable. In response to these challenges, there is an increasing demand for a unified and authoritative source for access management within the smart contract development landscape.

Smart Contract Development: Traditional Approach to AccessControl

Redefining Access Control with AccessManager

Contracts 5.0 offers a solution to address the evolving landscape of complex access control in decentralized protocols. AccessManager is a modern and efficient solution for role management across contracts.

Unlike traditional methods where each contract is managed separately, AccessManager empowers you to oversee permissions from a single contract. This streamlined approach not only simplifies the audit and control process but also brings a new level of transparency and flexibility to your smart contract development.

AccessManager excels at scoping permissions, ensuring that each function within a contract can be restricted to a specific role. These roles operate in a manner akin to the existing AccessControl framework, where multiple addresses can be granted one or more roles. Furthermore, each address granted a role can execute actions immediately or with a delay, facilitating time-locking capabilities without the need for additional smart contracts.

Smart Contracts Development: OzenZeppelin Contracts v5.0 AccessManager (Access Manager)

What's more, existing access control systems and DAOs utilizing Governor can seamlessly transition to AccessManager without requiring major upgrades. These changes are poised to significantly enhance transparency and flexibility throughout the secure development lifecycle.

It's worth noting that AccessManager support is on the horizon for OpenZeppelin Defender, offering an even more comprehensive suite of tools for smart contract development companies.

AccessManager support is coming soon to OpenZeppelin Defender. You can reach out to the OpenZeppelin team to request testing once it is available.

Elevating Audit and Testing Standards in Smart Contract Development

In the realm of smart contract development, stringent audit and testing practices are essential to ensure security and reliability. OpenZeppelin Contracts has consistently maintained an impressive unit test coverage of around 99%. In OpenZeppelin Contracts 5.0, this commitment to excellence is further underscored by the addition of more advanced testing practices.

Enhanced Testing Practices

Version 5.0 introduces an expanded suite of testing methodologies, including a set of fuzzing tests and additional formal verification rules. These enhancements are particularly noteworthy, with formal verification being applied to the novel Access Manager implementation.

A Rigorous Audit Process

In preparation for the launch of 5.0, an extensive audit of the entire codebase was conducted. The details of this comprehensive audit are readily available on our Contracts Security Center, providing transparency and confidence to developers and development companies alike.

Structured Audit Delivery and Review

Given the scope and complexity of this release, a structured process around audit delivery and review was deemed essential. OpenZeppelin successfully leveraged the OpenZeppelin Defender Audit module to streamline the review process, enabling the efficient tracking and resolution of all identified issues. This ensures that every aspect of the code is meticulously examined and perfected.

Public Engagement and Bug Bounty Program

To further strengthen security and engage with the developer community, OpenZeppelin introduced the Release Candidate to the public on September 19th. In a bid to encourage thorough testing, bug bounty awards were temporarily increased by 50%. The bug bounty program remains open, and the organization continues to actively invite interested developers to collaborate in the ongoing quest to discover and rectify potential vulnerabilities

Getting Started

For those embarking on new projects, OpenZeppelin Contracts v5.0.0 are available for both Hardhat and Foundry environments and within the OpenZeppelin Wizard.

Existing projects are encouraged to visit the upgrade guide, which advises the use of OpenZeppelin Defender's code module to ensure that dependencies are kept up to date, ensuring the utmost security and reliability.

The strong support and collaboration within the smart contract development community not only drive excellence but also promote innovation and sustainability. OpenZeppelin Contracts remains committed to its role as a community leader and a trusted partner in building the future of smart contract development.

Smart Contract Development With Rock’n’Block

At Rock'n'Block, we're dedicated to empowering blockchain projects with cutting-edge solutions, and we're thrilled about the release of OpenZeppelin 5.0. As a blockchain development company, our expertise extends to smart contract development and more. We understand the significance of secure and efficient smart contracts in the ever-evolving blockchain landscape. With OpenZeppelin's latest update, we're eager to assist projects in implementing and upgrading their smart contracts to ensure the highest levels of security and efficiency. Our commitment to excellence aligns perfectly with OpenZeppelin's vision, and we look forward to collaborating with projects to build a robust blockchain ecosystem.

Ready to elevate your smart contract development and blockchain projects? Reach out to our team and let's embark on a journey to build secure and efficient solutions together.

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