baseFeePerGas

baseFeePerGas is a per-unit price component used in Ethereum transactions since the London hard fork (EIP-1559). It represents the minimum amount of gas price, denominated in wei per unit of gas, that must be paid for a transaction to be included in a block. Unlike earlier models, this base fee is not paid to miners or validators; it is burned, reducing the circulating supply of ETH over time.

The base fee is determined by the protocol and updated every block. It is derived from the baseFee of the previous block and the actual gas used in that block relative to a target gas usage (the block’s gas target). If the block uses more gas than the target, the base fee increases; if it uses less, the base fee decreases. The rate of change is capped, so the base fee can adjust by at most a fixed percentage per block (commonly described as a 12.5% increase or decrease). This mechanism aims to stabilize transaction fees while still allowing price signals to reflect network demand.

Transactions must be priced with two fields: maxFeePerGas and maxPriorityFeePerGas. The actual fee paid per unit of gas is the sum of the baseFeePerGas and an additional priority fee chosen by the sender, up to their maximums. If a transaction’s maxFeePerGas is too low to cover the base fee plus priority, it may not be included.

Base fee dynamics and burning are central to Ethereum’s fee market, influencing fee predictability, network throughput, and ETH issuance.