Definition
Proposer-Builder Separation (PBS) is a blockchain consensus mechanism design in which the role of proposing blocks is logically separated from the role of constructing or “building” those blocks. Under PBS, specialized entities focus on assembling transaction bundles and optimizing block contents, while distinct block proposers, such as validators, are responsible for selecting and finalizing a block to be added to the chain.
In Simple Terms
Proposer-Builder Separation is a design where one party focuses on putting together the best possible block of transactions, and another party is responsible for choosing and proposing that block to the blockchain. It splits the responsibilities of building and proposing blocks into separate roles within the protocol.
Context and Usage
Proposer-Builder Separation is discussed in the context of mitigating centralization and information asymmetry around MEV extraction in modern blockchains. It is closely associated with the interaction between the execution layer, the mempool, and validators, and with designs that formalize or replace gas auction dynamics. PBS is often referenced in protocol research, MEV markets, and execution-layer architecture debates.