Introduction to userop.js

A simple JS library for building ERC-4337 UserOperations.

userop.js is an open-source library for building ERC-4337 UserOperations. Similar to how ethers.js allows developers to easily create traditional EVM transactions, userop.js allows developers to create and send UserOperations to ERC-4337 bundlers.

💪 Implementation agnostic: Can be used to create UserOperations for any ERC-4337 contract account.

🏗️ Intuitive design: Based on the builder design pattern, which mirrors how userOps are built in production.

Native TypeScript support: Builds on top of common ethers types like BigNumberish and BytesLike.


userop.js is available as an npm package here. To install, simply use your package manager of choice.

npm install userop
yarn add userop