What is Txn? It is precisely a **transaction (transaction)** on the Bitcoin blockchain. Txn fees are determined by two main factors: the transaction size (measured in virtual bytes - vB) and the fee rate you choose, with the current minimum being 1 sat/vB. This means the larger the transaction, the higher the fee will be. When you add more inputs or outputs to a txn, its size increases, leading to higher costs. Understanding this mechanism helps you optimize Bitcoin transaction fees more effectively.