What is double spending in Cryptocurrencies?

[Hernandez]

Hi there,

 I am new in Crypto and I am trying to learn different terms. I came across double spending and I didn’t understand it at all. Can someone explain it to me in a way I can understand?

[Jessica Kerry]

Hi there,
When a potential issue arises, and the same digital funds go to two recipients concurrently, that is double-spending. It is an attempt to spend one digital currency amount twice, creating a duplicate transaction.
Double spending is an obstacle digital currency must resolve to ensure the currency is not abused, thereby ensuring it maintains its trust and value. Such a system would call for countermeasures, in the form of protocols, to verify the payment you have received has not been spent elsewhere.
A solution came in the form of a bitcoin white paper that eventually become known as a blockchain. Essentially, this blockchain represents a database with unique properties. A participant, or node, runs a software enabling them to synchronize their database copy with peers. It ends in the entire network auditing transactions going back to the original block.
As such, public access to blockchain enables easy detection, and prevention, of fraudulent double-spending.

[Philip]

Double spending refers to the risk of successfully spending the same digital cash more than once. This can happen because digital files can easily be duplicated or falsified by tech-savvy individuals with a full understanding of the blockchain network. Just as with fake money, double spending can cause inflation as more fraudulent currencies are pumped into the market where they never existed before.
The value of the currency will also diminish as users lose trust in it and further lowers its circulation and retention in the market. In bitcoin, however, double spending is no longer a big problem, thanks to blockchain. Having all your transactions in the blockchain is proof that you own them, hence limit the possibility of double-counting among other frauds. The complex algorithms in blockchain transactions are hard to crack, making duplication and falsification hard to achieve.
However, double spending can still happen if the fraudster control more than 50% of the computational power of the blockchain network, hence can reverse transactions and create a blockchain that appears real. 
 

[Mason Ward]

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.