Double spending
Also · Double spend
Double spending is spending the same digital unit twice. Bitcoin prevents it without a central party by ordering transactions in a chain secured by proof of work.
Digital files copy for free, so a digital currency needs a way to stop the same unit being spent twice. Banks and payment networks solve this with a central database that decides which transaction came first. Bitcoin was the first system to solve it without that referee.
It does so by publishing transactions to every node, ordering them in blocks and making that order expensive to rewrite through proof of work. If 2 transactions spend the same UTXO, only 1 can enter the chain. The other is dropped. Confirmations measure how costly it would become to reverse that choice.
In French · Double dépense
