What is Double-Spending Problem?

The double-spending problem refers to a critical risk with digital currencies where the same funds can be copied and spent more than once. With fiat currency, the spender transfers physical cash to the receiver, unable to spend it again. With digital currency, blockchain systems are devised to prevent the same digital coin or token, such as bitcoin (BTC), from being sent to more than one address. The risk of double-spending with cryptocurrencies is mitigated by various mechanisms that verify the authenticity of all transactions.