What Is the Role of the UTXO Model in Preventing Double-Spending?
The Unspent Transaction Output (UTXO) model, used by Bitcoin, tracks every unspent output from previous transactions. A new transaction must reference these specific unspent outputs as inputs.
Since an output can only be spent once, the protocol inherently prevents double-spending. If an attacker tries to spend the same UTXO twice, the network will reject the second transaction as invalid because the input is already spent.
