What is Double-spend?
Spending the same coins twice. Preventing it without a trusted third party is the problem Bitcoin was built to solve.
Digital data copies perfectly, so any digital cash system must have a way to establish which spend came first. Before Bitcoin this required an issuer to keep the authoritative ledger.
Bitcoin replaces the issuer with proof of work: the ordering everyone accepts is the one with the most accumulated work behind it.
Related terms
Proof of work
The mechanism that secures Bitcoin: miners must find a hash below a difficulty target, which is expensive to…
How it worksConfirmation
A block containing your transaction. Each subsequent block adds another, making reversal exponentially more…
Transactions & feesRBF (replace-by-fee)
A signalling mechanism that lets an unconfirmed transaction be replaced by a version paying a higher fee.
This definition is part of the Bitcoin Logical glossary. For the fuller explanation, start with Learn, or see the live numbers on The Bitcoin Signal.