Last Irreversible Block (LIB)

The last irreversible block (LIB) is the last block validated on-chain and cannot be changed or modified. The block confirmation process is two-fold in blockchain protocols that use an asynchronous Byzantine Fault Tolerant (aBFT) consensus mechanism. First, block producers propose what’s called an irreversible block with a record of transactions. The proposed block then becomes irreversible if a majority of block producers acknowledge it, and the transactions are considered validated.