Byzantine Fault Tolerance (BFT)
A system's ability to reach agreement even when some participants fail or act maliciously — the core problem blockchains solve.
Byzantine Fault Tolerance is a system’s ability to function correctly even when some participants are faulty or actively malicious — named for the “Byzantine Generals Problem,” where generals must coordinate despite traitors sending false messages. It’s the theoretical heart of what every blockchain consensus mechanism achieves.
Classical BFT algorithms can tolerate up to one-third malicious participants and reach fast finality, which is why many modern Proof of Stake chains use BFT-style consensus (Cosmos’s Tendermint is a prominent example). The trade-off versus Bitcoin’s probabilistic approach is that BFT gives instant finality but typically requires a known, bounded validator set. Understanding BFT clarifies why different chains make different speed-versus-openness choices.