What Is a ‘Double Spend’ Attack and How Does the Blockchain Prevent It?

A Double Spend attack is the malicious act of spending the same cryptocurrency units more than once. The blockchain prevents this primarily through its consensus mechanism, like Proof-of-Work (PoW) or Proof-of-Stake (PoS).

Once a transaction is included in a block and confirmed by subsequent blocks, it becomes computationally or economically infeasible to reverse it, establishing a single, immutable history of ownership.