Smart contract

A smart contract is a program stored on a blockchain that runs automatically when its conditions are met, following rules in its code that cannot be changed once it is created. ethereum.org's introduction describes smart contracts as programs stored on the blockchain that follow "if this then that" logic and execute according to their code, and compares them to a vending machine: the right inputs guarantee the output, with no intermediary. The term was coined by Nick Szabo, who introduced the idea in 1994.

Airdrops run on them. The ARB airdrop was held and paid out by a Token Distributor Contract, and the airdrop ended on 24 September 2023; the Arbitrum Foundation's own tokens unlock through a vesting smart contract wallet. Claiming means sending a transaction to a contract, and approving one gives it power over your tokens: revoke.cash warns that an approved contract can spend them at any time. See token approval.