Bundler Services

Learn about the power of a Bundler and Alchemy's custom "Rundler"



Check out how to run our Bundler API here. To note, this is limited to private beta.

What is a Bundler?

EIP-4337 is bringing Account Abstraction to EVM chains. We anticipate that adoption of Smart Contract Wallets (SCWs) will increase significantly because of their advantageous user experience and flexibility. An essential infrastructure component supporting this shift from externally owned accounts (EOAs) to contract-based accounts is the Bundler, which forwards transactions to the SCW account.

The Bundler enables batched transactions for smart contract-based accounts. Batched transactions allow users of the wallet to perform multiple transactions in one single on-chain transaction. An important advantage is that batching transactions will save you time and money versus having to execute transactions one by one.

Read more on our blog post here

About Alchemy's Custom Built Rundler

  • Endpoints supported by “Rundler,” an Alchemy engineered ERC-4337 bundler.
  • Rundler is designed from the ground up for performance and leverages years of experience at Alchemy running scalable web3 infrastructure.
  • Our team is dedicated to pushing account abstraction forward in the Ethereum ecosystem and we’re working closely with the ERC-4337 community to tackle the next wave of challenges.
  • We’ll incorporate state of the art features as they’re released, and products will be battle-tested by traffic at scale.

We're proud to announce that we're open-sourcing Rundler, allowing the community to benefit from our expertise and contribute to its ongoing development.

Interaction with eth_estimateUserOperationGas

For accurate gas estimation, the paymaster portion of the User Operation validation contract call needs to run. When calling eth_estimateUserOperationGas it is recommended to use both a dummy signature (for the account portion) and a dummy paymasterAndData (for the paymaster portion). The dummy data is specific to the validation scheme of your account/paymaster. It does not need valid data, but it should not revert and should only fail with a signature error.

For the Alchemy paymaster, it is recommended to use the following dummy value in thepaymasterAndData before sending to eth_estimateUserOperationGas
DUMMY_PAYMASTER_AND_DATA = “0xc03aac639bb21233e0139381970328db8bceeb67fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff0000000000000000000000000000000007aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa1c”

Coming Soon

We are constantly working on expanding and enhancing our Bundler services. Here are some upcoming features we're excited about:

  • Full Alchemy API integrations on UserOperation hash:
    • Webhooks: Receive real-time notifications for events related to your UserOperations.
    • Simulation: Simulate the execution of UserOperations before submitting them to the network, to ensure correct behavior.
    • Subscription: Subscribe to pending UserOperations sent to Bundlers and bundled transactions sent from Bundlers.
    • Transfers: Get UserOperation metadata on Asset Transfer API requests.
    • NFT: Query NFT data using UserOperation indices and receiving UserOperation metadata.

Stay tuned for updates and announcements regarding these exciting features.

What’s Next

Start running our bundler services!