Definition

What is Checks-effects-interactions?

Checks-effects-interactions is the Solidity pattern of validating inputs first, updating your own state second, and calling external contracts last, which neutralises reentrancy.

By the time control leaves your contract, every invariant is already recorded, so a malicious callback finds nothing left to exploit. It costs nothing in gas and should be the default shape of any function that transfers value.

Definition by Adwait Keshari, founder of Monsmith.