Paymaster
A paymaster is an ERC-4337 contract that pays gas on a user's behalf — enabling gasless transactions, fees in any token, and dApps that sponsor their users
A paymaster is an ERC-4337 contract that pays gas on a user’s behalf — enabling gasless transactions, fees in any token, and dApps that sponsor their users’ onboarding. You sign intent; the paymaster settles the bill under programmable rules.
How it works
Inside ERC-4337’s flow, the paymaster contract validates sponsorship policy (allowlisted app? spending cap? token accepted?) and fronts the ETH. It can pull payment in ERC-20s, enforce per-user limits, or subsidize fully. Bundlers include the sponsored operation like any other.
Why it matters for decentralization
Paymasters remove crypto’s cruelest UX tax — “buy ETH before using anything” — without reintroducing custodians: policy is code, verifiable on-chain. The watch-point is dependence: if one paymaster subsidizes a whole ecosystem, its policy choices (and outages) become choke points. Diverse, competing paymasters keep the property that matters.
Risks & trade-offs
Sponsorship abuse (bots draining subsidies); paymaster centralization per app; policy bugs locking users out; and obscured true costs when fees hide inside “free” UX.
FAQ
Is gasless really free? No — someone pays (the app, a sponsor, or you in another token). “Gasless” means invisible, not absent.
Do I trust the paymaster? With your transaction flow, partially — it can refuse service but (in standard designs) can’t steal funds. Verify its policy code like any contract.
Paymaster vs relayer? Same idea, new standard: paymasters are the ERC-4337-native, permissionless version of old meta-transaction relayers.