Definition
BFT consensus is a class of fault-tolerant agreement mechanisms in distributed systems that remain correct and live even when a subset of participating nodes behaves arbitrarily or maliciously, up to a defined threshold. In blockchain contexts, BFT consensus specifies how validators propose, validate, and agree on blocks so that all honest nodes converge on the same sequence of state transitions despite Byzantine faults.
In Simple Terms
BFT consensus is a way for a network of computers to reliably agree on the same data, even if some of them are malfunctioning or acting maliciously. It sets strict rules so that honest participants still reach the same final result, as long as the number of bad actors stays below a certain limit.
Context and Usage
BFT consensus is discussed in the design and analysis of permissioned and certain permissionless blockchains, especially those prioritizing strong safety guarantees. It appears in protocol specifications, security proofs, and system models that formalize adversarial behavior and fault thresholds. The term is also used to categorize consensus families and to distinguish Byzantine-resilient mechanisms from weaker fault-tolerance models.