UTXO Model

The accounting model used by Bitcoin (and derived chains like Litecoin and Zcash) where balances are represented as a set of unspent transaction outputs rather than account balances. Each transaction consumes one or more UTXOs as inputs and creates new UTXOs as outputs; the difference between input and output values constitutes the transaction fee. The UTXO model enables natural parallelism and simple verification but makes stateful smart contracts more complex compared to account-based models like Ethereum or Solana.