ETH Glamsterdam upgrade activates on Sepolia testnet

TLDR

Ethereums Glamsterdam upgrade has activated on the Sepolia testnet, rehearsing a major scalability and efficiency upgrade before it reaches mainnet.

1. Sepolia has successfully forked to Glamsterdam, including a jump in its gas limit and new block-building rules, as a full-dress rehearsal for Ethereum (ETH) mainnet.
2. Glamsterdam introduces enshrined proposer-builder separation, block-level access lists and new gas pricing, all tested with blocks targeting around 200 million gas on Sepolia.
3. Next milestones are the Hoodi testnet fork and an eventual mainnet date; users should expect no immediate change in ETH fees, but the groundwork for larger future capacity is being laid.

Deep Dive

1. What Just Activated On Sepolia

Multiple reports confirm that Glamsterdam has gone live on the Sepolia public testnet at around 13:53 UTC, at epoch 353,024, after a coordinated client upgrade by node operators and validators. Sepolia now runs with Glamsterdam rules, including a much higher block gas limit, and serves as a low-risk environment where developers can stress-test the upgrade with valueless test ether before touching mainnet.

This Sepolia fork is described as one of the final major rehearsals before Glamsterdams eventual activation on Ethereum mainnet, with Hoodi identified as the next testnet stage and the mainnet date explicitly still to be determined. Sepolia results will guide whether client teams consider the upgrade ready for production on the base layer.

2. What Glamsterdam Changes Technically

Glamsterdam introduces three headline protocol features on Sepolia. First, enshrined proposer-builder separation (ePBS) restructures how validators interact with block builders, aiming to make block construction more efficient and resilient to MEV while giving validators more time to validate payloads. Second, block-level access lists record which accounts and storage slots are touched in a block, enabling clients to parallelize reads and some execution to better use modern hardware.

Third, gas pricing is being overhauled so that the cost of creating long-lived state (accounts and storage) is higher, while pure computation can become relatively cheaper. Sepolia is testing a gas limit of roughly 200 million per block, up from about 60 million, letting developers observe whether validators and clients can safely handle much larger blocks without breaking or centralizing around only very powerful machines. Reports explicitly note that higher capacity does not automatically guarantee lower fees for users.

3. What To Watch Next

Developers plan to review Sepolias behavior before scheduling Glamsterdam on Hoodi testnet and, later, on mainnet, with no firm mainnet timeline yet published. Validator client teams, such as Prysm, have already shipped releases tuned to the new 200 million gas limit and Glamsterdam rules, and other clients must remain in sync for reliable testing.

Rollups and L2s that settle on Ethereum are also preparing compatibility releases, so Glamsterdams mainnet activation will be a coordination moment across the broader ecosystem. Key risks to watch include hardware burden on validators, any bugs in ePBS or access lists, and whether gas repricing causes unexpected issues for smart contracts with hard-coded gas assumptions.

Conclusion

Glamsterdam going live on Sepolia is a critical step in Ethereums roadmap toward higher base-layer capacity and more nuanced gas economics. Nothing changes yet for users on mainnet, but successful Sepolia (and later Hoodi) runs would clear the way for a mainnet fork that could reshape how much activity Ethereum can safely handle per block and how that work is priced.