Rollup

A Rollup is a Layer 2 scaling solution that processes transactions off the main blockchain (Layer 1) and then posts the compressed transaction data or proof back to the main chain, such as Ethereum.

What is a Rollup?

In cryptocurrency and blockchain technology, a Rollup is a Layer 2 scaling solution that processes transactions off the main blockchain (Layer 1) and then posts the compressed transaction data or proof back to the main chain, such as Ethereum. Rollups aim to improve scalability, reduce gas fees, and increase transaction throughput while inheriting the security of the underlying Layer 1 blockchain.

Rollups are a critical component of the Ethereum scalability roadmap, enabling faster, cheaper transactions without compromising decentralization or security.

Types of Rollups

There are two main types of rollups:

  1. Optimistic Rollups – Assume transactions are valid by default and only run fraud proofs if challenged.
    • Examples: Optimism, Arbitrum
  2. Zero-Knowledge (ZK) Rollups – Use cryptographic proofs (ZK-SNARKs or ZK-STARKs) to prove that transactions are valid.
    • Examples: zkSync, Starknet, Scroll

Both types bundle many transactions together ("roll them up") and submit them to Ethereum as a single batch, dramatically reducing congestion and cost.

History and Evolution

The concept of rollups emerged as Ethereum faced scalability challenges due to high gas fees and network congestion. While the Ethereum community explored various Layer 2 options (e.g., Plasma, state channels), rollups gained momentum starting around 2019 as a more secure and general-purpose scaling method.

  • 2020–2021: Early rollup projects launched testnets and prototypes.
  • 2022 onward: Rollups became production-ready, supporting major DeFi apps and driving real user adoption.
  • Ethereum’s long-term roadmap, as outlined by Vitalik Buterin, centers on a "rollup-centric future", making them foundational to Ethereum’s scalability strategy.

Why Rollups Matter in Crypto

Rollups play a pivotal role in the transition from Ethereum as a single-chain system to a modular, multi-layered blockchain ecosystem. They allow:

  • Mass adoption of DeFi, NFTs, and dApps
  • Cost-effective transactions for users and developers
  • Scalable throughput without sacrificing decentralization

As the crypto ecosystem grows, rollups are expected to power millions of transactions per second across consumer applications, games, and financial services.