Polkadot’s Consensus Mechanisms

Learn all about Polkadot’s Consensus mechanisms.

Consensus refers to how a group of distributed, independent actors participate and agree on the state of the blockchain. Polkadot uses a hybrid consensus mechanism to split finality and the block production mechanism. This ensures probabilistic finality (ability to produce new blocks) and provable finality (having everyone agree on the state of the chain). Both mechanisms combined ensure blocks are produced rapidly, with a provable way to finalize the state of the chain, without any slowdown in transactions being processed. The two mechanisms are called BABE and GRANDPA.


BABE (Blind Assignment for Blockchain Extension) is the block production mechanism. It determines which validator nodes will produce blocks. BABE uses a verifiable random function (VRF) to randomly select a validator among all eligible candidates. This VRF is based on research published in the Ouroboros Praos paper, which is the current consensus mechanism used by the Cardano blockchain. This election is totally private, ensuring no validator can be coerced by an attacker at the time of block production.


(GRANDPA)(GHOST-based Recursive Ancestor Deriving Prefix Agreement) is the mechanism used to finalize blocks in the Relay Chain. This works by having ⅔ of the validators act honestly. As long as ⅔ validators attest to a chain containing a block, all blocks leading up to that are finalized.