Crypto glossary
Bundler
A bundler is the actor in ERC-4337 account abstraction that collects user operations from smart accounts and submits them on-chain as a regular transaction.
Smart accounts under ERC-4337 do not broadcast normal transactions. They sign user operations, which go to a separate mempool. Bundlers watch that mempool, simulate each operation to make sure it will pay, group several into one transaction and send it to the EntryPoint contract, which verifies and executes them. The bundler pays the gas upfront and is reimbursed by the accounts or their paymasters, keeping any difference as a fee.
Bundlers are core infrastructure for account-abstraction wallets, usually provided by the same companies that offer RPC nodes and paymasters, though anyone can run one. Their reliability decides whether a smart wallet's transactions land quickly. A shared, permissionless mempool between bundlers was introduced so that no single provider could censor or block user operations.
In memecoin slang, "bundlers" means something different: developers or insiders who buy a large share of a new token's supply across many wallets in the same block to hide concentration. That practice has nothing to do with account abstraction, which is why news reports need context to tell the two meanings apart.
Example
A user taps "send" in a smart wallet; the app passes the user operation to a bundler, which packs it with others and gets it included in the next block.