Ethereum’s next upgrade breaks the '21,000 gas' rule wallets rely on

Sending Ether will no longer always carry the same network fee, breaking one of Ethereum's oldest rules of thumb.

Developers from the Ethereum Foundation, the nonprofit that supports and maintains Ethereum, told wallet makers, blockchain trackers, and fee calculators in a blog post to update any software built on the assumption that a basic ETH transfer costs 21,000 gas units. Gas is how Ethereum measures the work a transaction asks the network to do, and users pay for that work in ETH.

Today, that 21,000 applies whether the receiving account has been used before or not. Under Ethereum's next major upgrade, Glamsterdam, sending to an existing account still costs 21,000, while sending to an address that has never appeared in Ethereum's records costs more because the network has to create and permanently store a new account.

The proposal puts that extra charge at 183,600 units of a new category called state gas.

Years of software have been built around that 21,000 as a fixed number. A wallet uses it to decide how much gas to attach to a payment, while a blockchain service uses it to sort transactions. Anything treating it as both the floor and the ceiling for an ETH transfer will reject valid payments or quote fees that come up short.

The reasoning is that the two are not the same amount of work. Paying an account that already exists only adjusts balances Ethereum is tracking anyway, while paying a fresh address adds a record its computers may have to hold forever. Both have carried the same charge until now.

Developers still have time to find the problems. Glamsterdam switches on Thursday on Platåberget, a practice version of Ethereum that uses worthless tokens so developers can break things safely. It reaches two more test networks — Sepolia and Hoodi — after that, and then the real Ethereum.

Nobody sending ETH needs to do anything this week. The warning is aimed at the companies whose software those users depend on.