ERC-4337 is a new Ethereum standard that enables account abstraction, allowing for gasless transactions, batched transactions, social logins, and more. As the ecosystem around ERC-4337 grows, several bundler packages have emerged, each with its own strengths and weaknesses.

Stackup Bundler

Yes, we're mentioning ours first.

The Stackup bundler is a highly performant Golang bundler designed for easy integration with Go Ethereum (geth), and as of February 2023 one of only two bundlers on this list fully compliant with ERC-4337. It is actively maintained and has extensive documentation, making it the go-to option for most teams. Stackup offers access to hosted bundlers on their website, so you don't need to self-host a bundler. This is a great option if you want a high performance and battle-tested option with active support, or a hosted solution.

Infinitism Bundler

Written in typescript and developed by the original ERC-4337 authors, the ETH Infinitism reference bundler is a reliable and fully compliant option for developers. It was developed alongside the specification test suite also maintained by the ETH Infinitism team. This is a great option if you prioritize compliance with the ERC-4337 specification over performance.

AA-bundler

Vid Kersic, an ETH Protocol Fellow, is developing a Rust-based bundler for ERC-4337. This bundler is a great option for integration with other Rust tools.

Skanda

Skanda is a Typescript bundler developed by Etherspot. Etherspot is actively involved in the development of the ERC-4337 bundler mempool specification. The bundler is under active development and expected to be ready in March 2023. This is a great option if you are already leveraging Etherspot's SDKs for your application.

Candide Wallet Bundler & Paymaster RPC

Developed by the Candide team for the Candide wallet, the Candide-bundler-and-paymaster-RPC is a Python implementation of the ERC-4337 bundler. This bundler is a great option if you are developing on top of Candide's open source wallet.

Which is best?

Each of these bundlers offers unique features and benefits, making it important for developers to carefully evaluate each option and choose the one that best fits their needs. As of February 2023 only two meet the ERC-4337 specification and pass the test suite: Stackup and ETH-Infinitism. The Stackup bundler is usually the best option of the five bundlers in development, but as the ERC-4337 ecosystem continues to grow we can expect to see more bundler options emerge, offering even greater flexibility and functionality to developers.