Double spend protection refers to measures that prevent the same digital currency unit from being spent more than once. This is crucial because, unlike physical cash, digital currencies can theoretically be duplicated or reused.To achieve double spend protection, most systems use a ledger, such as a blockchain, which records all transactions in a transparent and immutable way. When a transaction is made, it’s grouped with others into a block and added to the chain. Once a block is confirmed by the network, the transactions it contains are considered valid and irreversible.Additionally, consensus mechanisms help verify transactions. In most cases, multiple participants (nodes) in the network must agree on the validity of transactions. This collective validation reduces the likelihood of fraud.Overall, double spend protection ensures trust within the system, allowing users to transact confidently, knowing that their currency can’t be fraudulently spent multiple times.