Although Stackup takes care of account infrastructure, you still have a number of decisions to make about which pieces you want to use if you are developing an application with ERC-4337.

These decisions can be overwhelming, so here's the advice we find ourselves giving 80% of projects.

👍

No endorsements

We have no endorsement agreements with any third parties listed here. These are based purely off of our experience developing applications with ERC-4337, and will change with time.

Architectural Decisions

Most apps will need to make three major decisions: how users will authorize transactions, what account contracts to give users, and what SDK to use to build user operations.

You can see a template application that uses all of these recommendations here

Decision 1: Authorization method

We recommend using Web3Auth or similar MPC methods for basic applications. It has a plug-and-play modal that you can insert directly into your app, and users can always still connect with a traditional wallet.

More advanced authorization methods include session keys, biometrics, and device keys. You can explore some common authorization services here.

Decision 2: Smart account contracts

We recommend using ZeroDev's Kernel smart account for most applications. It is the most mature ERC-4337 Smart Account specific implementation, and includes modules for session keys and recovery methods.

It is also relatively future-proof. It is designed to comply with ERC-6900, a standard for making ERC-4337 smart accounts and their plugins interoperable.

See more options here.

Decision 3: SDK for building user operations

We recommend using userop.js rather than using an ecosystem-dependent SDK for building transactions. Userop.js is more flexible, MIT open-source licensed, and likely underpins any application-specific SDK you are using.

See more options here.

Optional: Paymasters

We recommend using a paymaster service rather than build one yourself. If you build one yourself, you need to manage on-chain liquidity.

We recommend the Stackup Paymaster, not just because we built it, but because it is the most reliable and can be used to accept ERC-20 for gas payments or to sponsor transactions outright.

Regardless, in most instances it is better to use a paymaster that approves the gasless transaction off-chain than using one that is fully on-chain. This design allows a user to do any type of transaction without needing a blockchain's native token first - i.e., a user can start with just an ERC-20 token in their account.

If you use a paymaster to sponsor transactions for your app, we strongly recommend having a separate API key just for sponsoring transactions with your paymaster so that you can put business logic for which transactions you will accept server-side.

Bonus: Reading user operation data

ERC-4337 User Operations are routed through the EntryPoint contract, so they need to be parsed differently than regular transactions. We recommend using a data API that processes this data for you. Our Data API does a lot of this parsing for you, but if you want more information you can use a service like JiffyScan.

JiffyScan's block explorer is a bit slow, but has the most features.