What Are Layer 2s and Why Are They Important?

July 31, 2023

We take a deep dive into the blockchain's secondary protocols.

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Layer 2 solutions, often referred to as "Layer 2s," are secondary protocols built on top of a blockchain (Layer 1) to increase its capacity and speed. They are an essential part of the blockchain ecosystem, providing scalability solutions that allow networks to handle higher transaction volumes while maintaining security and decentralization.

The Blockchain Layers

What is Layer 1?

Layer 1 refers to the underlying main blockchain architecture. In the context of Ethereum, for example, Layer 1 is the Ethereum mainnet where all transactions are processed and finalized. It is the base-level where the blockchain's most fundamental processes occur, including transaction validation and consensus mechanism.

What are Layer 2s?

Layer 2s are protocols built on top of Layer 1 to improve its functionality. They handle transactions off the main chain, thereby reducing congestion and improving transaction speed and scalability. Layer 2 solutions include rollups, sidechains, and state channels, among others.

Why Do We Need Layer 2?

As blockchain networks grow, they often struggle with scalability issues. Layer 1 can only process a limited number of transactions per second (TPS), leading to slower transaction times and higher fees. Layer 2 solutions address these issues by taking transactions off-chain, allowing for more transactions to be processed simultaneously, reducing fees, and improving overall user experience.

How Does Layer 2 Work?

Layer 2 solutions work by taking transactions off the main chain, processing them, and then recording the final state on the main chain. This allows for many transactions to be processed in a single batch, significantly reducing the load on the main chain.

Layer 2 Rollups

Rollups are a type of Layer 2 solution that bundle or "roll up" multiple transactions into a single one, which is then posted to the main chain. There are two main types of rollups: Optimistic Rollups and ZK Rollups.

Optimistic Rollups

Optimistic Rollups are a Layer 2 solution that assumes good faith among network participants. They allow transactions to be processed instantly, with the final verification and posting to the main chain happening later. If a fraudulent transaction is detected, it can be challenged and removed.

ZK Rollups

ZK Rollups, on the other hand, use zero-knowledge proofs to validate transactions off-chain before posting them to the main chain. This method provides a higher level of security and scalability, as it doesn't rely on the assumption of good faith.


Sidechains are separate blockchain protocols linked to the main chain. They allow for transactions to be processed independently from the main chain, thereby increasing the overall transaction capacity of the network.


Validiums are similar to ZK Rollups, but they store data off-chain, providing even greater scalability. However, this comes at the cost of some degree of decentralization.

Key differences between Layer 1 & 2

Layer 1 and Layer 2 are both integral components of blockchain technology, but they serve different purposes and have distinct characteristics.

Here are the key differences between them:

1. Functionality:

  • Layer 1: This is the base layer of a blockchain network. It includes the blockchain protocol itself, which defines the rules of the network, including transaction validation and consensus mechanisms. Layer 1 is where all transactions are processed and finalized.
  • Layer 2: Layer 2 solutions are built on top of Layer 1 to enhance its functionality. They handle transactions off-chain, thereby reducing the load on the main chain and improving transaction speed and scalability.

2. Scalability:

  • Layer 1: Scalability is a significant limitation of Layer 1. Due to the decentralized nature of blockchain, every transaction must be validated by every node in the network, which can be time-consuming and resource-intensive. This limits the number of transactions that can be processed per second.
  • Layer 2: Layer 2 solutions address the scalability issue by taking transactions off-chain. This allows for many transactions to be processed simultaneously, significantly increasing the transaction capacity of the network.

3. Security:

  • Layer 1: Layer 1 provides a high level of security as all transactions are validated by every node in the network. This makes it extremely difficult for malicious actors to manipulate the system.
  • Layer 2: While Layer 2 solutions also aim to maintain the security of the network, the level of security can vary depending on the specific solution. For example, sidechains may have a different level of security than the main chain, while rollups rely on the security of the main chain for final transaction validation.

4. Decentralization:

  • Layer 1: Layer 1 is fully decentralized, with every node in the network participating in the validation of transactions.
  • Layer 2: Layer 2 solutions can vary in their level of decentralization. Some, like state channels, maintain a high level of decentralization, while others, like certain types of rollups or sidechains, may involve some trade-offs in decentralization for increased scalability.

5. Use Cases:

  • Layer 1: Layer 1 is suitable for transactions and applications that require a high level of security and decentralization, but it may not be practical for high-volume or low-cost transactions due to scalability limitations.
  • Layer 2: Layer 2 solutions are ideal for high-volume, low-cost transactions and complex decentralized applications. They expand the use cases of blockchain technology by improving scalability and reducing transaction costs.

Why Are There So Many Layer 2s?

The variety of Layer 2 solutions is a response to the different needs and requirements of various applications and use cases.

Each Layer 2 solution offers a unique balance between scalability, security, and decentralization.

Examples of Common Layer 2s and their products:


Optimism uses Optimistic Rollups to improve the scalability of Ethereum, allowing for faster transaction times and lower fees.

Popular products on Optimism:

  1. Velodrome
  2. AAVE V3
  3. Sonne Finance

Arbitrum One

Arbitrum One also uses Optimistic Rollups, but with a unique approach to dispute resolution and data availability.

Popular products on Arbitrum One:

  1. GMX
  2. Radiant
  3. Stargate Finance

Polygon zkEVM

Polygon zkEVM is a decentralized Layer 2 scalability solution for Ethereum. It utilizes cryptographic zero-knowledge proofs to provide validity and fast finality to off-chain computations.

Popular products on Polygon zkEVM:

  1. Obvious Wallet
  2. QuickSwap
  3. Mobula API

*Note that many products adopt a multi-chain approach and are available on multiple chains.

In conclusion,

Layer 2 solutions play a crucial role in the evolution of blockchain technology, providing the scalability needed for mainstream adoption while maintaining the security and decentralization that make blockchain unique.

Watch this video to learn more about Layer 2 Scaling:


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