Rollup
A rollup is a Layer 2 scaling system that processes many blockchain transactions off-chain and posts a compressed summary back to the main chain.
A rollup is a Layer 2 scaling method that helps a blockchain handle more transactions without making every user compete for space on the main chain. It collects many transactions, processes them outside the base blockchain, and then posts a compact record back to it. The main chain still provides security and final settlement, while the rollup reduces the amount of data and computation that must happen directly on-chain.
Rollups matter because they can lower fees and speed up everyday activity such as token swaps, NFT minting, or payments while still relying on a major blockchain like Ethereum for security. There are two common designs: optimistic rollups, which assume transactions are valid unless challenged, and zero-knowledge rollups, which submit cryptographic proof that the transactions were processed correctly. A practical comparison is packing many letters into one envelope: the main chain handles the envelope, while the rollup organizes the contents more efficiently.
Other terms in Layer 2 & Scaling
Data Availability
The assurance that the transaction data needed to verify a blockchain or layer 2 network can be accessed by anyone who needs it.
Fraud Proof
A fraud proof is evidence submitted to a blockchain to show that a proposed transaction result or rollup state is invalid.
Layer 2
A Layer 2 is a secondary network or protocol built on top of a blockchain to process transactions faster and cheaper while relying on the main chain for security.
Layer 3
A Layer 3 is an application-specific blockchain layer built on top of a Layer 2 to add customization, scalability, or specialized features.