What is Tendermint (BFT)?

Tendermint is a Byzantine Fault Tolerant consensus protocol designed by Jae Kwon in 2014, widely used through the Cosmos SDK for building application-specific blockchains. The protocol combines a round-robin proposer selection with a two-phase voting process: prevote and precommit. In each round, a designated proposer broadcasts a block, and validators proceed through the prevote phase (where they vote on whether the proposed block is valid) and the precommit phase (where they commit to the block if they received prevotes from more than two-thirds of validators). A block is finalized when more than two-thirds of validators send precommit votes for it. If any round fails to produce a finalized block, the protocol advances to the next round with a new proposer.

Tendermint provides instant finality — once a block is committed, it cannot be reverted, which eliminates the possibility of chain forks. The protocol tolerates up to one-third of validators being Byzantine while maintaining both safety and liveness under partial synchrony assumptions. Block times are typically 5-7 seconds, though this is configurable. Tendermint's design separates consensus from application logic through the Application Blockchain Interface (ABCI), allowing any application to use Tendermint as its consensus and networking layer. This modular design was revolutionary in blockchain architecture, enabling developers to focus on application logic without implementing consensus from scratch. Validators are weighted by stake, and proposer selection is proportional to voting power.

Tendermint powers the Cosmos Hub and the broader Cosmos ecosystem, which includes hundreds of blockchains built with the Cosmos SDK, including Osmosis, Injective, Celestia, dYdX, and Cronos, among many others. The protocol was developed by Tendermint Inc. (later renamed Ignite) and has become one of the most widely deployed BFT consensus engines in the blockchain industry. The Inter-Blockchain Communication (IBC) protocol, built on top of Tendermint's instant finality guarantees, enables trustless cross-chain communication between Cosmos chains. In 2023, the Tendermint consensus engine was renamed to CometBFT as part of its transition to community governance, but the underlying protocol remains fundamentally the same.