Gas Limit

Every transaction you submit to a blockchain carries with it an instruction about how much computational work you are willing to pay for at maximum. That ceiling is called the gas limit. It is your way of telling the network: “Go ahead and process this transaction, but do not spend more than this many units of gas on my behalf.”

The gas limit exists as a safety mechanism. Imagine you are interacting with a smart contract and that program contains a bug or an unexpected loop that could run forever. Without a gas limit, such a transaction could theoretically drain your entire wallet trying to complete an impossible task. The gas limit ensures that once a set amount of computational effort has been used, the transaction simply stops. If the transaction completes successfully before hitting the limit, you are refunded the unused gas. If it runs out of gas before finishing, the transaction fails and you lose only the gas that was consumed up to that point. Most wallets like MetaMask automatically estimate an appropriate gas limit for you.

Example: Think of the gas limit like the budget you set before going shopping. You tell yourself, “I will spend no more than $100 today.” If you find everything you need for $75, great — you keep the rest. But if the store runs out of what you need and you have already spent $100 without completing your shopping, you go home empty-handed, having still spent the money on the attempt.