What Is a “Race Attack” and How Does It Differ from a Standard Double-Spend?

A race attack is a simpler form of double-spend where the attacker attempts to spend the same coins in two conflicting transactions almost simultaneously. They send one transaction to a merchant (e.g. for goods) and a second, conflicting transaction (e.g. back to their own wallet) to the network's miners with a higher fee.

The goal is to have the second transaction confirmed first, invalidating the first. Unlike a standard 51% attack, a race attack does not require majority hashrate; it relies on network latency and the miner's fee-maximizing behavior.