David Tso
Growth & Customer Success

Polygon zkEVM, Scroll, and Linea, Ethereum’s New Scaling Frontier

Setting the Stage

Let’s discuss the latest buzzword in the world of crypto and web3: zkEVM. It’s the latest upgrade to zero-knowledge (zk) rollups, an Ethereum Layer 2 (L2) solution. While the discourse around zkEVMs has been filled with announcements of announcements, it’s now becoming more tangible as zk rollup development teams are starting to take concrete steps to implement it. This is an exciting breakthrough for the entire industry, as general-purpose zkEVMs have the potential to significantly improve the scalability of Ethereum.

The month of March has seen major milestones for zkEVMs, with the introduction of new projects and significant progress made by existing ones. Below are a few key events from the past month:

• March 3: Scroll launched the Alpha version of its zkEVM on Ethereum’s Goerli Testnet.

• March 27: Polygon launched the Mainnet Beta version of its zkEVM, making it available to a wider audience.

• March 28: ConsenSys unveiled its own zkEVM, Linea, and opened its Public Testnet to developers and users.

As we can see, zkEVMs have made impressive strides, and Covalent has been on a roll integrating with them as they are widely regarded as the ultimate scaling solution for Ethereum. Today, we will explore the different types of zkEVMs, the top teams developing zkEVMs with EVM-equivalence, and the onchain data behind their adoption and traction. By the end of this blog post, you will have a better understanding of why zkEVMs are gaining eyeballs as a game-changing technology for the future of Ethereum.

zkEVMs Have Entered the Chat

To understand why zkEVMs are the holy grail of scaling Ethereum, we first need to take a step back and look at the current state of Ethereum L2 solutions. At present, there are two main types of L2s: optimistic rollups and zk rollups. Both aim to increase throughput and lower transaction fees by processing transactions off Ethereum’s L1, while still leveraging Ethereum for settlement and data availability. This allows for computation to take place offchain while proofs of the computation happening accurately are uploaded onchain. The primary difference between optimistic rollups and zk rollups lies in how they validate transactions:

• Optimistic rollups: assume all transactions are valid by relying on other actors to submit fraud proofs during a one-week settlement period to the Ethereum Mainnet.

• Zk rollups: validate all transactions by using mathematically verifiable proofs that can settle on the Ethereum Mainnet immediately.

Compared to optimistic rollups, zk rollups are often regarded favourably due to their advantages in transaction finality and withdrawal times (no one-week settlement period), allowing users to bridge faster between rollups or back to the Ethereum Mainnet. However, optimistic rollups have gained more adoption in the L2 space because they were initially easier to implement and compatible with the Ethereum Virtual Machine (EVM), enabling the easy porting of code and toolings from L1 to L2 – which is great UX. In contrast, zk rollups started with custom virtual machines that were application-specific, making it challenging for developers and users to adopt them. However, with the launch of zkEVMs, the landscape is now changing.

The zkEVM represents a significant breakthrough for Ethereum L2s. By enabling zk rollups to be EVM-compatible and general-purpose, developers and users can enjoy the same functionality as Ethereum’s L1, while reaping the benefits of zk technology. This puts zk rollups on a path to challenge their optimistic rollup counterparts, aligning with Vitalik Buterin’s 2021 prediction that zk rollups, with their inherent advantages, would eventually outcompete optimistic rollups. As the technology continues to evolve, zkEVMs are expected to gain significant traction in the coming months.

Types of zkEVMs

There has been an ongoing friendly rivalry between optimistic and zk rollup teams to develop the best Ethereum scaling solution. However, another race is brewing within the zk rollups sector itself – an informal competition to see which team can be the first to develop Type 1 and Type 2 zkEVMs.

In August 2022, Vitalik Buterin introduced classifications to map out zkEVMs based on EVM-compatibility. According to Buterin’s classification:

• A Type 1 zkEVM: is fully equivalent to Ethereum. It can reuse 100% of the EVM infrastructure, and it can even be used to upgrade Ethereum itself. However, this type of zkEVM has the longest prover (part of the code that generates zk proofs) times, as no modifications are made to speed up zk proof generation.

• Type 2 zkEVMs: are fully EVM-equivalent. However, they trade full Ethereum-equivalency for faster prover times and easier development. While a few Ethereum dapps may be incompatible with this type of zkEVM, improved prover times are crucial for faster finality of rollup transactions.

• A Type 3 zkEVM: has further changes to improve proof generation and make building on it easier. While this type of zkEVM could be compatible with most Ethereum dapps, some may require rewriting.

• A Type 4 zkEVM: can only compile some EVM code and be compatible with some Ethereum dapps, but not the EVM itself. However, it has the lowest costs and fastest prover times of all zkEVM types.

EVM-compatibility enables blockchain compatibility with Ethereum, but the developer experience may differ, requiring the rewriting of smart contracts or the reimplementing of lower-level code. On the other hand, EVM-equivalence ensures full bytecode (executable code on EVM) compatibility with Ethereum, meaning that any smart contract or developer tool from the Ethereum ecosystem can be used on the EVM-equivalent network too – which is a big advantage for developers. EVM-equivalence also simplifies the migration of Ethereum-based dapps and enables easier interoperability with EVM dapps on other L1s or L2s. Therefore, the goal of a zkEVM is to have full EVM-equivalence or a Type 2 zkEVM, while the truest form of a zkEVM is to reach full Ethereum-equivalence or a Type 1 zkEVM.

Although a Type 1 zkEVM may take some time to develop due to its complexity, several teams are currently working on Type 2 zkEVMs. Polygon zkEVM, initially a Type 3 zkEVM, is undergoing upgrades to become a Type 2 zkEVM. Similarly, Scroll is also working towards achieving a Type 2 zkEVM, having started as a Type 3 zkEVM. In contrast, Linea already falls under the Type 2 zkEVM classification, being fully bytecode-compatible with Ethereum and allowing developers to easily port their code without any major changes.

Teams Working on zkEVMs

Now, let’s take a closer look at the development teams leading the way for zkEVMs, which include Polygon zkEVM, Scroll, and Linea. While these zkEVMs are not an exhaustive list, they are the ones currently supported by Covalent and offer a good representation of the general-purpose zkEVMs that are aiming for greater EVM-equivalence and not just compatibility. As you read on, I encourage you to dive deeper into any projects that pique your interest, as new advancements are constantly emerging in this rapidly-evolving field. The table below summarizes the latest information on Polygon zkEVM, Scroll, and Linea as of April 2023:

Polygon recognized the limitations of its Proof-of-Stake (PoS) sidechain and has been working towards a more efficient zk-based blockchain. In August 2021, Polygon announced a $1 billion strategic fund to invest in the development of zk-related technology. The same month, it acquired Hermez Network for $250 million to collaborate on building a zkEVM, which was later rebranded to the current Polygon zkEVM. On March 27, 2023, Polygon launched the Polygon zkEVM Mainnet Beta, meeting its targeted launch date of Q1 2023 and making it accessible to all developers and users. Polygon zkEVM uses SNARKs to verify the accuracy of STARKs, combining the speed of STARK proofs with the compact size of SNARK proofs to combine multiple proofs into a single proof. This not only reduces costs and latency but also improves scalability.

While Scroll may not be as well-known as some of the other development teams, it has been collaborating with the Ethereum Foundation’s Privacy and Scaling Explorations group and making considerable progress. In March 2023, Scroll announced a successful $50M fundraising round at a $1.8B valuation. On March 3, 2023, Scroll took a major step forward by launching the Alpha version of its zkEVM on Ethereum’s Goerli Testnet. One of Scroll’s key differentiators is its use of a modified version of ZCash’s “Halo2” code, which allows protocols to harness the benefits of SNARKs’ small proof size and quick proof verification, while removing the need for a trusted setup – the Achilles’ heel of SNARKs. In addition, Scroll is committed to decentralization and already has plans in place to decentralize its prover network and sequencer after the launch of its Mainnet, aligning with the ethos of the Ethereum community.

Linea is the newest zkEVM to enter the playing field. It’s been in development by ConsenSys R&D since 2019 and is powered by ConsenSys – the software giant behind several of the most widely used products in crypto, including MetaMask, Infura, and Truffle. On March 28, 2023, Linea introduced its Public Testnet to the world. Linea runs on SNARKs but utilizes a unique stack resulting from years of research by ConsenSys R&D. Their internally-generated and lattice-powered prover helps to circumvent the key flaws in SNARK technology, allowing for the quick generation of SNARK proofs without requiring a trusted setup. Linea also aims to tackle the rollup training wheel problem by implementing a multi-prover rollup, which involves multiple prover implementations generating validity proofs at varying security levels. This approach mitigates the risk of a single point of failure present in single-prover rollups, resulting in enhanced security and reliability.

Polygon zkEVM Adoption

While Polygon zkEVM Mainnet Beta just launched last month, it’s already experiencing significant growth in usage. According to Covalent data, users have bridged slightly more than $5M in funds to Polygon zkEVM.

The future looks bright for Polygon zkEVM as it continues to attract popular DeFi protocols such as Uniswap, Balancer, and Hop to its network. In addition to this, it will also be used to underpin Immutable zkEVM’s infrastructure, which aims to revolutionize web3 gaming. With these developments, we can expect Polygon zkEVM to play a significant role in DeFi and gaming moving forward.

Scroll Adoption

After 1.6M transactions processed on its Pre-Alpha Testnet, Scroll released its Alpha Testnet, and it’s seeing very healthy traction so far. According to Covalent data, the Scroll Alpha Testnet has gained over 3M unique wallet addresses since its launch. However, it’s worth noting that the surge in unique wallet addresses could be due to speculation around an upcoming token launch, as Scroll has hinted at creating an incentive mechanism to encourage network participation.

Scroll has distinguished itself by its commitment to developing its zkEVM transparently and collaboratively. The Scroll Alpha Testnet offers a great opportunity for developers and users to contribute to Scroll’s development as it marches toward its Mainnet launch.

Linea Adoption

Linea’s Public Testnet is now live, with external users being onboarded at a rapid pace. According to Covalent data, the Linea Goerli Testnet has seen over 600K unique wallet addresses sign up.

Developers are deploying dapps on Linea using familiar tools such as MetaMask, Infura, and Truffle, just as they would on Ethereum. On top of this, ConsenSys’ established reputation in the crypto space has enabled it to secure partnerships with protocols such as Lens, Celer, and Cashmere, among others. These partnerships are expected to contribute to Linea’s future growth.

The Dawn of a New Blockchain UX Era

For years, the Ethereum community has embraced the idea that zk rollups are the most promising scaling solution. However, it was not until recently that a general-purpose zkEVM capable of running all current Ethereum dapps became available. The introduction of Polygon zkEVM, Scroll, and Linea has provided developers and users with a new frontier to explore.

As Ethereum progresses toward its goal of scaling, the introduction of a Type 1 zkEVM remains on the horizon. In the meantime, zkEVMs ranging from Type 2s to Type 4s offer unique customizations and UX enhancements for developers and users alike. As these solutions continue to mature and the dapps on them continue to grow, there is potential for zkEVMs to outcompete optimistic rollups and become the leading scaling solution for Ethereum. Now the race is on to see which of these first-movers can implement their zkEVM at scale and onboard developers and users as quickly as possible to generate network effects.

Are you ready to explore these cutting-edge zkEVM platforms? Covalent’s Unified API offers developers easy access to onchain data and enables integration with 100+ chains, including Polygon zkEVM, Scroll, and Linea. With our API, you can streamline your development process and stay ahead of the curve. Get your Free API Key and start building the next generation of dapps today!

Quote from Grace Torrellas, Product Lead at Polygon zkEVM

“General-purpose zkEVMs are the trailblazers for scaling the Ethereum ecosystem in a trustless and censorship-resistant manner that inherits Ethereum’s security. The Polygon zkEVM team has shipped a fully functional zkEVM with a working and open-sourced proving system that has been battle tested. We are proud to be amongst the firsts advancing the use of the zk tech focusing on scaling Ethereum.” 

Quote from pseudotheos, Researcher at Scroll

“At Scroll, we believe that zkEVMs are the future of scaling, and that something as complex as a zkEVM should be built in the open, together, with the community. zkEVMs are at the frontier of zk research, and our goal is to collaborate on building a zkEVM with the same open-source ethos that is at the heart of Ethereum.”

Quote from Declan Fox, Product Lead at Linea

“At Linea, we’re dedicated to pushing the boundaries of blockchain scalability and efficiency. Our zkEVM rollup solution leverages the power of zero-knowledge proofs and the EVM to enable highly scalable and secure smart contracts. By integrating with Covalent, we’re able to provide developers with a seamless data-driven experience, empowering them to build the next generation of decentralized applications. We’re thrilled to be working alongside Covalent, as together we can drive Ethereum’s scalability to new heights and unlock unprecedented opportunities for the global web3 developer community.”

Quote from Ganesh Swami, Co-Founder and CEO at Covalent

“Ethereum’s ongoing efforts to achieve scaling through protocol upgrades can often face significant delays due to their technical complexity. Fortunately, our partners Polygon zkEVM, Scroll, and Linea are actively addressing pain points for Ethereum in its quest for scalability, security, and enhanced functionality. As a core infrastructure provider for the Ethereum ecosystem, Covalent is honoured to collaborate with these visionary teams. We look forward to seeing the exciting possibilities that will unfold in the years ahead.”

Written by David Tso.

Covalent (CQT) is shipping data infrastructure for the decentralized ecosystem, solving Long-Term Data Availability for Ethereum—infrastructure that can re-execute blobs and shape AI. With CQT staking now back on Ethereum, The New Dawn of network expansion towards the Ethereum Wayback Machine commences. Today, this means AI use cases have unfettered access to onchain data from over +225 blockchains and growing.

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