Can smart contracts be modified or deleted once deployed?

Once deployed on a blockchain, smart contracts are immutable—meaning they cannot be modified or deleted. This is a core feature of blockchain technology: the code is permanent and transparent. However, developers can design upgradeable smart contracts using proxy patterns, allowing them to update logic while keeping the contract address the same. Some contracts include self-destruct functions, but these are rare and typically require specific conditions. This immutability provides security and trust—users know the rules won't suddenly change. However, it also means bugs or vulnerabilities cannot be patched after deployment, which is why thorough testing and audits are crucial before launching smart contracts.