Bundlers

A Bundler is a specialized node that listens for UserOperations from your application, groups them together into a single standard Ethereum Transaction, and submits them to the blockchain.

Why do we need Bundlers?

Smart Accounts don’t send Transactions directly. Standard Ethereum transactions must be signed by an EOA and paid for in ETH.

Instead, Smart Accounts sign UserOperations — intention objects that define what the user wants to do. But an intention object isn’t an Ethereum transaction, so miners/validators won’t process it.

A Bundler bridges this gap. It operates an EOA, collects UserOperations from the mempool, bundles them into an array, and sends a single standard Transaction to the global EntryPoint contract, paying the ETH gas fee itself.

How the economics work

Why would a Bundler pay gas for your users? Because it gets reimbursed:

1. You send a UserOperation to the Bundler.
2. The Bundler wraps it in a standard transaction and pays the ETH gas to the network.
3. The EntryPoint contract processes the transaction.
4. The EntryPoint charges the user’s Smart Account (or their Paymaster) enough ETH to cover the gas.
5. The EntryPoint refunds the Bundler’s EOA with the collected ETH, plus an optional premium.

The 0xGasless Bundler

The 0xGasless SDK uses our high-performance, globally distributed Bundler infrastructure by default. We operate nodes across all supported networks to ensure your UserOperations are mined quickly and reliably.

When you pass a bundlerUrl to createSmartAccountClient, you’re telling the SDK where to send the user’s signed UserOperation.

const BUNDLER_URL = "https://bundler.0xgasless.com/11155111" // Sepolia