In cryptocurrencies and digital currencies, double spending refers to the risk that a digital currency can be spent more than once. This can happen because digital information can be easily reproduced. To prevent double spending, blockchain technology was created, which ensures the integrity and traceability of transactions using a decentralized ledger. When a transaction is made, it is added to a block, which is then verified by network nodes. If someone attempts to create a duplicate transaction, the network can identify and reject it.