What Is the “Supermajority” Requirement in Most PoS Systems and Why Is It Used?

The supermajority requirement in most Proof-of-Stake (PoS) systems is typically two-thirds (2/3rds) of the total staked tokens. This threshold is used because it is the minimum required to achieve Byzantine Fault Tolerance (BFT) consensus.

If less than one-third of the validators are malicious, the honest two-thirds can still reach agreement and finalize blocks. This threshold ensures that a small minority of attackers cannot halt the network or force a malicious chain finality without risking the slashing of their massive stake.