What is double spending in Cryptocurrencies?

Hi Hernandez,

Double-spending refers to a potential problem in the digital currency system where the same funds are transferred to two recipients at once. It is a risk that can undermine the protocol as participants can’t verify that the funds they’ve got haven’t been spent somewhere else.
With cryptocurrencies, it is very important to make sure that specific units can’t be duplicated. This is a risk that must be prevented at all costs, otherwise, the entire system would be compromised. 

Bitcoin (BTC) is particularly good at preventing double-spending. With Bitcoin, the users have to wait for transaction confirmation in a block, which means that there’s no easy way for the sender to undo the transaction. They could undo it by reversing the blockchain which demands an absurd amount of hash power.