Ethereum is warning wallet providers, block explorers, exchanges, custody platforms and fee calculators that Glamsterdam will end the long-standing assumption that a basic ETH transfer always costs 21,000 gas. Under the new model, transfers to existing addresses will remain at 21,000 gas, but sending ETH to an address that has never appeared in Ethereum's state will trigger an additional 183,600 units of state gas because the network must create and permanently store a new account record. The change alters a convention embedded in Ethereum tooling since the network launched in 2015. Software that treats 21,000 gas as both the floor and ceiling for ETH transfers could reject otherwise valid payments, underprice transactions or cause transfers to fail once Glamsterdam reaches mainnet. The Ethereum Foundation said developers should review code for hard-coded gas values and test updates on devnets and testnets. Glamsterdam is set to activate first on Platåberget before moving to Sepolia and Hoodi and eventually mainnet. The upgrade was initially targeted for the first half of the year but was pushed to the fourth quarter to allow more testing and preparation. Beyond this transfer-cost change, Glamsterdam also includes broader gas repricing and other protocol updates already being exercised on Platåberget.