Blockchain Developer Certification 2025 – 400 Free Practice Questions to Pass the Exam

The "data" field in a contract transaction contains the compiled bytecode of the contract. When a smart contract is deployed on a blockchain, it consists of executable code that defines the logic and operations of that contract. This bytecode is what the Ethereum Virtual Machine (EVM) processes when executing transactions involving the smart contract.

When you initiate a contract transaction, the data field is used to carry out specific function calls within that smart contract. This can include invoking particular methods and passing parameters necessary for those methods, all represented in the form of bytecode.

In contrast, other options are part of a transaction but serve different purposes: the sender's address identifies the origin of the transaction, the amount of value indicates any Ether being transferred, and the nonce ensures the uniqueness of the transaction in relation to previous ones sent by the same sender. However, none of these represent the executable code of the contract itself, making the compiled bytecode the correct answer regarding the contents of the data field in a contract transaction.