What Is a Crypto Layer 2 And How Does It Work?

What Is a Crypto Layer 2 And How Does It Work?

In understanding blockchain technology, it's crucial to start at the foundation, known as "Layer 1" (L1). This layer represents the bedrock of decentralized networks such as Bitcoin (BTC) and Ethereum (ETH). These platforms operate on distributed ledger systems that facilitate the ownership and exchange of digital assets without the need for intermediaries. The absence of third-party reliance means that anyone can operate the L1 protocol using a personal computing device, like a laptop or even a Raspberry Pi.

At the heart of Layer 1 is the consensus mechanism, which assures all participants, or nodes, in the network to eventually reach an agreement on the system's state — for instance, confirming the amount of ETH owned by a user at any given time. Currently, the Bitcoin network's Layer 1 can process approximately seven transactions per second, while Ethereum's capacity is slightly higher, but still limited to tens of transactions per second. These limitations result in a competitive scramble for block space.

This competition manifests in the form of transaction fees, with users outbidding each other to have their transactions prioritized and confirmed more rapidly on the blockchain. The higher the fee offered by a user, the sooner their transaction is likely to be processed. This bottleneck in throughput has often led to congestion and higher costs, presenting a significant challenge in terms of scalability.

While the intrinsic balance among decentralization, security, and scalability — often referred to as the Blockchain Trilemma — seems to be a fundamental constraint, Layer 2 solutions have been developed to tackle these limitations. Technologies such as rollups for Ethereum and the Lightning Network for Bitcoin are designed to enhance the transaction capacity and efficiency of these networks, offering a promising avenue to overcome the hurdles inherent to their Layer 1 counterparts.

The Layer 2 Chronicles: Steps Towards Blockchain Scalability

Users of cryptocurrencies frequently encounter steep fees and delayed transactions due to the network reaching its processing limit, which currently stands at around 1.5 million transactions per day and only about 15 transactions per second. High-traffic events, such as Yuga Labs' Otherside virtual land sale or the 2021 bull market, exemplify the network's congestion and consequent fee spikes and sluggish application performance.

Layer 2 solutions, or "L2s," are the technological innovations designed to ease this bottleneck. Acting as supplementary highways to Ethereum's bustling mainnet, these L2s offer expedited and cost-efficient transactions while still benefiting from the underlying network's security and decentralized nature. Think of L2s as arterial roads that run alongside the main blockchain thoroughfare, complete with on/off ramps for easy access, providing a swift alternative to the congested main roads.

Arbitrum, Optimism, and zk-Sync are leading the charge as popular L2 networks on Ethereum, while the Lightning Network performs a similar function for Bitcoin users. Collectively, these networks hold a market cap nearing $2 billion, reflecting their critical role in blockchain scalability.

Layer 2s distinguish themselves not only by reducing fees through bundling transactions off-chain but also by expanding utility due to their ability to process more transactions per second at a lower cost. This allows for enhanced user experiences and a broader range of applications, ultimately aiming to rival the efficiency of centralized payment processors like Visa and Mastercard.

The integration of L2s is essential in addressing the decentralization-related scalability issues inherent in blockchain systems. Where traditional banking systems benefit from centralized control for more efficient payment regulation, blockchain must maintain security and transparency across thousands of network participants. In this context, Layer 1 takes on the role of ensuring security and decentralization, while Layer 2 focuses on scaling transaction capabilities, together working towards a network that is not only faster but also more user-friendly, ensuring that blockchain technology can meet the demands of global marketplaces and perhaps, one day, become superior to traditional financial conduits.

How does layer 2 work?

Layer 2 (L2) protocols serve as an advanced framework for Ethereum, designed to handle transactions off the main Ethereum network (Layer 1), while leveraging the robust security that the main blockchain provides. These Layer 2 solutions are separate blockchains that complement and extend the functionality of Ethereum, providing a scalable environment where the network can operate more efficiently.

The ingenuity of L2 solutions lies in their ability to take a significant load off of Layer 1. This not only reduces congestion but also improves the overall scalability of the system. One of the key technologies within Layer 2 is the concept of rollups. Rollups work by grouping hundreds of transactions into a single Layer 1 transaction, effectively sharing and minimizing the transaction fees among all users included in the rollup. While these transactions are executed off of Layer 1, their data is still posted to Layer 1, which ensures the security of Ethereum is upheld—reverting a transaction within a rollup would necessitate reverting a transaction on Ethereum itself.

There are two primary forms of rollups: optimistic and zero-knowledge. Both types differ in the method they use to submit transaction data to Layer 1, but the goal remains the same—to ensure the fidelity and security of transaction data while offloading the bulk of the computational work.

Beyond rollups, Layer 2 also includes sidechains and other frameworks that support a multitude of applications. Some L2s are designed to be open and accessible, supporting a wide array of applications, whereas others are more specialized, catering to specific project needs. Regardless of their structure, the essential feature of all Layer 2 solutions is their ability to post transaction data back to Layer 1, where it is securely anchored in the blockchain's ledger and historical record.

The Layer 2 space is a dynamic field with varying levels of accessibility and application. By offloading the workload from Layer 1 and posting transaction data back to it, Layer 2 protocols enhance the functionality, speed, and efficiency of the Ethereum network, while maintaining the integrity and security that come with blockchain technology. This dual-layer architecture ensures that as Ethereum continues to grow and evolve, it can meet the demands of its users and applications without sacrificing its foundational principles.

There are a few kinds of rollups, each with its own nuances. For instance, Optimistic and ZK (Zero-Knowledge) rollups differ in how they communicate with the main chain.

Optimistic rollups

Optimistic rollups operate alongside the primary Ethereum blockchain. They process transactions on a parallel track before reporting the outcomes to the main chain. Users favor these rollups because of their lower fees. If there’s any suspicion of a fraudulent transaction, it can be challenged and verified through fraud proofs, which reconstruct the transaction using the existing state data. While the resolution process may take longer compared to ZK rollups, transactions within the Optimistic rollup itself are confirmed swiftly.

Optimistic rollups are also fully compatible with the Ethereum Virtual Machine (EVM), meaning they can mirror any function from the Ethereum mainnet onto their layer. Some prominent instances of Optimistic rollups include solutions like Arbitrum, Optimism, and Boba.

ZK rollups

In contrast, ZK rollups employ cryptographic proofs to ascertain transaction integrity. These proofs, known as validity proofs—including SNARKs and STARKs—are presented to the main chain. ZK rollups update the state of transfers on their layer using these proofs without needing full transaction data, streamlining the validation process. Upon the acceptance of a validity proof by the rollup contract, the accuracy of the transactions is already assured, simplifying the movement of funds back to the main chain. However, ZK rollups have limitations, such as partial EVM support and greater computational demands for certain operations. Examples of ZK rollups include platforms like dYdX, Loopring, and zkSync.


While sidechains like XDai and Polygon PoS run in tandem with the Ethereum network and offer EVM compatibility, they rely on their own consensus mechanisms and aren't secured by the Ethereum mainnet, classifying them outside the strict definition of Layer 2. These chains mimic Ethereum functionality but with a distinct security model that entails different risks, especially concerning trust in the sidechain operators.


Validiums utilize validity proofs akin to those in ZK rollups but differ by not storing transaction data on the main chain. They can operate several chains in parallel, each capable of processing thousands of transactions per second. However, due to their need for more specialized programming languages, support for smart contracts is more limited.

Both sidechains and validiums, although not true Layer 2 solutions like rollups, offer similar benefits such as reduced transaction fees and high processing capacity. They provide alternative scaling methods but come with distinct security considerations due to their separate operational frameworks.

Future of L2 blockchains

As the blockchain ecosystem evolves with an increasing focus on mainstream adoption, scalability solutions are becoming more crucial. Ethereum's Layer 1 (L1) advancements, such as the shift to a Proof of Stake consensus mechanism and the introduction of sharding, are expected to significantly enhance the performance of connected Layer 2 (L2) networks. These L2 solutions are poised to offer unprecedented transaction speeds and cost reductions, further enabling the growth of decentralized applications, particularly in the DeFi sector.

The advancement of L2 solutions will be instrumental in fostering a multichain environment, enhancing blockchain interoperability and facilitating new possibilities in digital asset trading. As the number of bridges between L2 platforms expands, users stand to gain from a seamless experience and the opening of new pathways in blockchain interactions.

However, the path towards a decentralized landscape is not without its complexities. While L2 protocols are ideologically committed to decentralization, the practical deployment often involves centralized elements. This is evident in scenarios such as the Lightning Network for Bitcoin, where despite its decentralized protocol, users tend to favor custodial wallets and services for the sake of convenience. Similarly, many Ethereum L2 solutions start with centralized features, intended to be gradually decentralized over time, enabling quicker updates and development in the early stages.

For blockchain users, discerning the true extent of decentralization within these protocols is challenging. Projects like L2Beat provide critical insights into the decentralization status of Ethereum’s L2 networks, underscoring the importance of diligent research and a cautious approach when navigating the crypto space.

As the industry progresses, collaboration and innovation will be key to delivering L2 solutions and decentralized applications (DApps) that advance the world towards a decentralized economy, while upholding the foundational principles of security, decentralization, and scalability.

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