Calldata

Calldata refers to a special area of memory in the Ethereum Virtual Machine (EVM) where input data for smart contract function calls is stored. It’s read-only and is mainly used to pass arguments from an external call to a smart contract. Unlike other types of data storage like memory or storage, calldata is more cost-efficient because it’s not modifiable and doesn’t persist beyond the function execution.

How Calldata Works in Smart Contracts

When a user or another contract calls a smart contract function, the inputs—such as numbers, addresses, or strings—are encoded and included in the transaction’s calldata. Solidity, the most widely used smart contract language, allows developers to specify function arguments with the calldata keyword to minimize gas costs. This is particularly useful for functions that don’t need to modify input data.

Why Developers Use Calldata

Using calldata helps optimize gas fees, especially in contracts that handle large arrays or repeated function calls. Since calldata is immutable, it also adds a layer of security by preventing unintended changes to the input data during execution.