A smart contract holds its own balance and its own state, and executes its code when a transaction invokes it. Every node runs the same code on the same inputs and reaches the same result, so the outcome is agreed by the network rather than decided by whoever deployed it. This is the machinery underneath DeFi, tokens, NFTs and DEXs alike.
Determinism cuts both ways. A contract cannot be persuaded, but nor can it be corrected: once deployed, its code usually cannot be changed, and a bug is exploitable by anyone who spots it, permanently. Upgradeable designs exist but reintroduce an administrator who can change the rules — which is a trust assumption, not the absence of one.
Can a smart contract be changed after deployment?
Not usually. Contracts are immutable by default; upgradeable patterns exist but give some party the power to alter behaviour, which is itself a risk to weigh.
Last updated October 17, 2026