Block Builder
A block builder is an entity responsible for aggregating transactions from the mempool and private bundles into a candidate block. They optimize the block content to maximize their revenue, primarily through MEV extraction and transaction fees.
Builders compete to have their blocks proposed and validated by the network, often engaging in sophisticated bidding wars. This role is central to the protocol physics of modern blockchains, as builders essentially dictate the order of execution for all on-chain activity.
They must balance profitability with network requirements like gas limits and block size constraints. The emergence of specialized builders has transformed the landscape of block production, shifting it toward a more professionalized and competitive market.
Their decisions directly impact the settlement speed and cost for all network users.