Calldata

Calldata is a specific form of read-only memory data used by smart contracts to call external functions. Once a rollup has batched enough transactions, it’s expected to post this state transition change in a compressed form to the L1 via calldata. Rollups currently use L1 calldata for data storage, which is limited to ~10KB per block. They do this so anyone can reconstruct the chain and verify the latest state. Posting the calldata on-chain allows Ethereum and its robust, decentralized network of nodes to “check the work” done off-chain. Instead of doing the computation, the calldata lets the Ethereum mainnet quickly and easily verify that everything done off-chain was valid and accept the state changes, i.e., double-check the work.