What a paymaster kit does
A paymaster kit is a software layer built on top of ERC-4337 that allows decentralized applications to pay gas fees on behalf of users. This process, known as gas sponsorship, removes the need for users to hold native tokens like ETH to interact with a blockchain. Instead, the paymaster contract covers the transaction costs, enabling smoother user experiences and broader adoption of Web3 applications.
In the ERC-4337 ecosystem, the paymaster acts as a sponsor for user operations. It verifies that the transaction meets certain criteria before paying the bundler that processes the block. This separation of concerns allows developers to implement flexible payment models. For instance, users can pay gas fees using ERC-20 tokens such as USDC rather than the network's native currency. Projects like MetaMask Smart Accounts and Alchemy’s paymaster infrastructure demonstrate how this abstraction works in practice, allowing dapps to subsidize costs or require alternative payment methods.
The kit provides the necessary smart contract logic and integration tools to deploy these paymaster contracts. By handling the complex verification and payment routing internally, the kit ensures that user operations are executed correctly without requiring the end user to manage multiple asset balances. This foundational component is essential for building account-abstraction-enabled wallets that feel as intuitive as traditional web applications.
Calculate your gas sponsorship costs
Estimating the financial impact of ERC-4337 gas sponsorship requires modeling your specific user activity against current network conditions. Using the Paymaster Kit, you can sponsor transactions directly or allow users to pay in ERC-20 tokens, but the cost structure depends on three variables: the number of active users, their transaction frequency, and the prevailing gas price on the target chain.
Use the calculator below to project your monthly operational expenses. Input your expected daily active users (DAU), average transactions per user, and the current gas price in gwei. The tool applies a standard overhead multiplier to account for the paymaster's execution costs and buffer, giving you a realistic baseline for budgeting.
Note that this estimate assumes a base gas limit of 21,000 units per transaction. Complex smart contract interactions may require significantly more gas. For accurate forecasting during high network congestion, consider adding a 20-30% buffer to your calculated costs to prevent user experience failures due to underfunded paymasters.
Top Paymaster Kit Implementations
Choosing the right paymaster kit depends on your chain selection and whether you need to sponsor gas in ETH or ERC-20 tokens. Below are the leading implementations for ERC-4337 gas sponsorship in 2026.
Biconomy Paymaster
Biconomy offers a modular paymaster solution that simplifies ERC-20 gas payments. Their kit allows developers to integrate gas sponsorship with minimal code, supporting major EVM chains like Ethereum, Polygon, and Arbitrum. The implementation is designed for ease of use, making it a strong choice for teams prioritizing quick integration over deep customization.
Stackup (Alchemy) Paymaster
Stackup, now part of Alchemy, provides a robust paymaster infrastructure for account abstraction. Their solution supports both sponsored transactions and ERC-20 fee payments, leveraging Alchemy's extensive node network for reliability. Stackup is particularly favored by large-scale dApps that require high throughput and consistent uptime for user operations.
SafeCore Paymaster
SafeCore offers a paymaster implementation tailored for multi-signature wallets and social recovery accounts. This kit is ideal for projects where security and account ownership are paramount. It integrates seamlessly with Safe wallets, allowing users to pay gas fees in ERC-20 tokens while maintaining the familiar Safe user experience.
OpenGSN (Deprecated but Legacy)
While OpenGSN was an early pioneer in gas abstraction, it is largely deprecated in favor of ERC-4337-native solutions. New projects should avoid OpenGSN and instead use modern paymaster kits that support the latest bundler and entry point standards.
Comparison of Key Features
| Paymaster Kit | ERC-20 Gas Support | Supported Chains | Integration Complexity |
|---|---|---|---|
| Biconomy | Yes | EVM (Multi-chain) | Low |
| Stackup | Yes | EVM (Multi-chain) | Medium |
| SafeCore | Yes | EVM (Multi-chain) | Medium |
Developer Tools for Paymaster Integration
To streamline the development and testing of your paymaster implementation, consider these resources:
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| Feature | Biconomy | Stackup | Safe{Core} |
|---|---|---|---|
| ERC-20 Gas | Yes | Yes | Yes |
| Multi-sig Support | No | No | Yes |
| Free Tier | Yes | Yes | Yes |
ERC-20 gas payment vs native sponsorship
Choosing how to pay for transaction fees affects both user experience and your project's operational costs. ERC-4337 paymasters allow dapps to abstract gas fees entirely. You can choose between sponsoring gas in the native token (like ETH) or allowing users to pay with ERC-20 tokens (like USDC).
Native token sponsorship
When you sponsor gas in ETH, the paymaster covers the entire fee on behalf of the user. This approach offers the simplest integration because it relies on the base layer's native currency. Users do not need to hold the specific token to transact, reducing friction for new onboarding. However, this model requires your project to maintain a reserve of ETH to cover operational costs.
ERC-20 token payment
ERC-20 gas payment enables users to pay gas fees using stablecoins or other tokens they already hold. This method aligns better with user expectations in DeFi, where holding stablecoins is common. According to MetaMask's documentation, this setup allows users to pay gas in USDC directly from their smart accounts, improving accessibility for non-Ethereum holders. Alchemy notes that paymasters can handle these conversions, though it adds complexity to the sponsorship logic.
Comparison of approaches
The following table outlines the technical and economic differences between the two methods.
| Feature | Native (ETH) | ERC-20 (USDC) |
|---|---|---|
| User Balance Required | No (dapp pays) | Yes (user holds tokens) |
| Integration Complexity | Low | Medium (requires swap logic) |
| Cost Predictability | High | Variable (gas + spread) |
| Best For | New user onboarding | DeFi and existing holders |
Common paymaster: what to check next
The term "paymaster" carries baggage from traditional finance and legal escrow, which often confuses developers building on-chain experiences. In the context of ERC-4337, a paymaster is strictly a smart contract utility, not a human intermediary or a legal trust account.
Is a paymaster legitimate?
Yes, ERC-4337 paymasters are legitimate and increasingly standard for user experience optimization. They are not scams or hidden fees; they are transparent smart contracts that sponsor user operations (UserOps). Major wallets like MetaMask integrate them to allow gas sponsorship in ERC-20 tokens like USDC, removing the friction of holding ETH for gas (MetaMask Docs).
What is a paymaster used for?
Paymasters abstract gas fees to improve onboarding and retention. They allow dApps to:
- Sponsor transactions: Pay gas for users to complete specific actions (e.g., first-time minting).
- Tokenize gas: Let users pay transaction fees in stablecoins or other ERC-20 tokens instead of the native chain token.
- Batch operations: Enable complex multi-step workflows where the dApp covers the cumulative gas cost.
How does a paymaster differ from an escrow?
The difference is functional, not just semantic. An escrow agent holds funds until conditions are met, acting as a trusted third party for asset transfer. A paymaster is a gas-relayer contract that signs and submits UserOps on behalf of a user. It does not hold user principal funds; it only covers the network cost to execute the transaction. Attorneys often serve as paymasters in legal contexts using IOLTA accounts, but on-chain, the "paymaster" is code, not a person.
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