A transaction fee (Transaction Fee, TxFee) is an operational charge that a user pays to the blockchain network when transferring cryptocurrency. This payment motivates miners or validators to include the operation in the next block and thereby confirm it. In essence the fee plays a dual role: it rewards the participants who keep the network running and protects the blockchain from spam and overload with useless operations.

The size of the fee is not fixed and is formed dynamically. It depends on the current load of the network, the amount of data in the transaction and the priority chosen by the sender. When the network is overloaded, users compete for a place in a block and fees rise; in calm periods they fall. Many wallets allow the fee to be set manually, affecting the speed of confirmation.

What the fee size depends on

• the network load and the number of pending transactions;
• the "weight" of the operation — the amount of data and the number of inputs and outputs;
• the chosen priority and the desired speed of confirmation;
• the rules of the specific blockchain and its consensus mechanism.

Understanding the principles of fee formation helps to plan transfers rationally: choosing a less busy time or an adequate priority so as not to overpay while not waiting too long for confirmation.