Paymaster (gas sponsorship)

In the ERC-4337 account-abstraction system, a user's smart account sends a user operation instead of a normal transaction. That operation can name a paymaster: a contract that has deposited ETH with the shared EntryPoint contract and agrees to cover the gas. Before paying, the paymaster runs its own rules, for example checking that the app has whitelisted the user, that a daily budget is not exceeded, or that the user has approved a token payment it will collect instead.

Paymasters are the engine behind gasless onboarding. Games, social apps and consumer wallets sponsor fees so new users can act without first buying ETH, and some paymasters let people pay fees in USDC on layer 2 networks. Infrastructure providers sell paymaster services with dashboards and spending policies, and since EIP-7702 ordinary addresses can use them too.

Sponsorship is not free: the app or provider pays and may limit, meter or end it at any time. Badly configured paymasters can be drained by spam or griefing. Paying gas in tokens usually includes a markup over the real network fee.