Overview

Alchemy’s Bundler—also known as “Rundler”—is an open‑source, Rust‑based implementation of an ERC‑4337-compliant bundler designed to streamline smart contract wallet operations. It enables developers to batch user operations (userOps) into a single transaction, sponsor gas fees, and monitor user‑initiated operations through a powerful API and dashboard. As the leading bundler in the ecosystem, it supports multiple chains (Ethereum, Optimism, Arbitrum, Polygon, Base, Zora, Frax, Polynomial, Shape) and handles millions of transactions, making it an ideal solution for Web3 apps requiring scale and reliability.

Features and Capabilities

• Built for scale & reliability: Written in Rust; powers 60M+ on-chain transactions as ecosystem’s #1 bundler.
• ERC‑4337 compliance: Fully supports account abstraction and bundled user operations.
• Optimized gas estimation: Provides accurate gas and fee computations to reduce costs.
• Batch transactions: Enables combining multiple actions (e.g., approvals, swaps, NFT purchases) into a single atomic transaction.
• Historical lookup: Trace any past user operation from genesis across supported chains.
• Real‑time webhooks: Get notified when userOps land on-chain, facilitating instant updates and UI sync.
• Debugging tools included: Diagnose and resolve failed user operations directly via Alchemy Dashboard.
• MEV protection: Integrates MEV shielding for chains with reliable private transaction infrastructure.
• Multi-chain support: Compatible with Ethereum, Optimism, Arbitrum, Polygon, Base, Zora, Frax, Polynomial, Shape.
• Bundler API endpoints: Exposes JSON-RPC methods (e.g., eth_sendUserOperation, eth_estimateUserOperationGas, eth_getUserOperationByHash, eth_supportedEntryPoints) ideal for deep integration.
• Open‑source repository: Code fully available under an open-source license to self‑host and customize.