Crypto payment gateways prevent double-spending attacks by waiting for blockchain confirmations before marking a payment as complete. Every transaction is verified by the blockchain network and added to an immutable ledger, making it nearly impossible to spend the same funds twice. Many gateways also use real-time transaction monitoring, fraud detection mechanisms, and configurable confirmation thresholds based on the blockchain being used. By validating each transaction before processing an order, businesses can significantly reduce the risk of fraudulent or duplicate payments.