A multi-signature account is a smart contract that requires multiple owners to approve transactions before they can be executed. Instead of one person controlling the funds with a single private key, the smart contract enforces that multiple people must sign off before any transaction goes through.

Modern multi-sigs like Safe use off-chain signatures - owners sign messages without publishing each signature as a transaction. Once enough signatures are collected, anyone can execute the transaction on-chain, meaning it is submitted to Ethereum. The executor pays gas, and some setups reimburse it from the multi-sig.

In this 3-of-4 example, at least 3 out of 4 owners must sign to approve a transaction. Try it yourself in the demo: connect to the multi-sig contract, propose a transaction, and watch how 3 different owner wallets need to approve before the smart contract executes it. Notice how the 4th owner doesn't need to sign - this flexibility means you don't lose access to funds if one owner loses their wallet.