Transaction fee is an amount associated with processing a transaction and including it in a block. The exact fee mechanism depends on the blockchain.

In some networks, the fee depends strongly on the amount of transaction data rather than the value being transferred. This is particularly visible in UTXO systems, where transactions with many inputs can require more block space.

Why fees change

When block capacity is limited, users compete for inclusion in available blocks. Higher demand can increase the fees required for faster confirmation. Some protocols use explicit fee markets or priority mechanisms to determine which transactions block producers select.

A transaction fee is distinct from mining electricity costs or other operational expenses. It is an economic mechanism of the blockchain itself and may be distributed among network participants according to protocol rules.