The London hard fork implemented EIP-1559 and introduced Ethereum’s fee-burn mechanism.
Ethereum activated the London upgrade on 5 August 2021. Its best-known change, EIP-1559, replaced the old fee-market model with a protocol-set base fee that adjusts according to network demand. Users can also offer a priority fee, or tip, to the block proposer. The base fee is burned, meaning it is permanently removed from Ethereum’s supply rather than paid to the validator or miner.
EIP-1559 was designed to make transaction-fee estimates more predictable, not to guarantee permanently low fees. During heavy congestion, the base fee can still rise sharply. The upgrade also introduced variable-sized blocks and changed gas-refund rules through other included Ethereum Improvement Proposals.
London is often confused with The Merge, which moved Ethereum from proof of work to proof of stake in September 2022. The Merge did not introduce fee burning; that mechanism had already gone live with London. Istanbul, Constantinople, and Byzantium were earlier Ethereum upgrades with different technical changes.