Gloas for the consensus layer; Amsterdam for the execution layer. Put them together and you get Glamsterdam, Ethereum’s next major upgrade, which notably just passed its first primetime test.

That’s because Glamsterdam went live on the Sepolia testnet yesterday, October 6th, with the chain finalizing blocks through the cutover without any critical hiccups.

It’s just testnet activity for now, sure. But what it bodes is considerable for the OG smart contract network. As Ethlabs researcher Barnabé Monnot said on the news:

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Ethereum Foundation researcher Toni Wahrstätter echoed that sentiment, too, calling Glamsterdam the opening for Ethereum’s "biggest throughput increase since launch."

Indeed, going by the numbers, Glamsterdam is built for a ~200M gas limit, a ~3.3x jump from today’s 60M in one upgrade. For perspective, mainnet sat at 30M for years before validators took it to 60M across three bumps in 2025, and even the London upgrade's doubling of the max block size back in 2021 kept the target at 15M.

Still, the fork itself won’t flip a switch that instantly makes Ethereum 3x bigger. Instead, it’ll change how blocks get made so that much bigger blocks become safe to produce, and then validators will decide whether to raise the limit.

All that said, let’s break down what specifically is changing for Ethereum here and what’s left before mainnet. 

Glamsterdam’s big ideas

The fork bundles 18 EIPs in total, but three of these proposals will do most of the heavy lifting.

The first, of course, is enshrined proposer-builder separation, or ePBS for short. To oversimplify a great deal, this mechanism will grant Ethereum validators more time.

Most Ethereum blocks today are built by specialized builders and then passed to validators through trusted middlemen called relays. With EIP-7732 (ePBS), the proposer instead commits to a builder's signed bid, and the builder reveals the full block afterward.

This means that the act of checking a block's transactions no longer has to be crammed into the ~4 second attestation window. Per the EIP, most validators will henceforth get ~9 seconds instead.

The next significant pillar coming in Glamsterdam will be block-level access lists, or BALs. In short, these lists will offer a new capacity for parallel work.

For context, today Ethereum clients mostly walk a block's transactions one by one, since they can't know ahead of time what each one will touch. Thus EIP-7928 (BALs) will make every block ship with a map of all the state it touches, plus the values afterward.

With that guide in hand, clients can prefetch data and validate transactions in parallel. To use a factory metaphor, ePBS is akin to giving quality control more time for inspections, while BALs give the floor everything it needs so several assembly lines can run at once.

Additionally, bigger contracts, plus some repricing, are coming. EIP-7954 is set to raise the max contract size from 24 KiB to 64 KiB, easing a cap that has long forced big apps to split their code up.

Meanwhile, the fork will raise the price of what's meant to be scarce, i.e. new state. Under EIP-8037, creating a fresh storage slot jumps from 20,000 to 97,920 gas, while a plain ETH transfer to an existing account stays at 21,000 under EIP-2780.

Checking on Sepolia and the road to mainnet

Sepolia’s first Glamsterdam block landed yesterday with a 60M gas limit, i.e. the same cap that Ethereum mainnet runs today. From there, Sepolia's limit hit the 200M target roughly 11 hours after the fork and has held onto that mark since.

Each block's proposer can only nudge the gas limit by about 0.1% per block, so if every proposer had nudged it up on every block, Sepolia could've made the trip in ~4 hours. It took more than twice that long instead, likely in part because two popular consensus clients, Prysm and Teku, kept validators at 60M after the fork unless they explicitly opted into 200M.

The aforementioned Wahrstätter has since shared early numbers suggesting the levers are already paying off. He found every client now handles each unit of gas faster than before the fork, e.g. a 40M gas block that took Geth ~115 ms to execute now takes ~30 ms.

It's less than one day of data from one node per client, but it's definintely a promising start.

As far as what comes next, with Sepolia out of the way it’s Ethereum’s Hoodi testnet that’s on the slate for the ensuing Glamsterdam deployment. Oct. 27th has been tentatively floated for this activation, but that’s not set in stone yet, and mainnet remains a target for some point in Q4 2026.

Remember, too, that Glamsterdam was originally penciled in for the first half of 2026, and Sepolia's own fork slipped from Aug. 3rd to Oct. 6th. Thus it’s entirely possible we’ll see the timeline fluctuate some more from here.

More scale, more potential

To be sure, we’ll face new dynamics and new questions with the arrival of Glamsterdam.

For example, some Ethereum tools will break if they don’t stay current with the fork’s changes. The EF has warned that wallets, indexers, and gas estimators that assume a hard max gas limit will have to be updated to avoid problems.

Additionally, with the repricing around growing state, onchain activity that creates lots of new accounts or storage (e.g. airdrops, mints, and fresh wallets) will pay more, while everyday transfers won't.

Yet these intricacies will prove to be minor points. The broadest and most significant dynamic at work here is that the Ethereum L1 is about to get much roomier, and that’s great news for Ethereum ecosystem experiments, whether big or small, TradFi or weird.

For instance, back in August I noted that Fake World Assets briefly became mainnet’s largest gas consumer on one of its wildest days. Glamsterdam should give surges like that far more room to breathe without pricing everyone else out.

In other words, Ethereum is getting more room for more dreams, more projects, more activity. Now, let’s see how the Ethereum community can fill it toward both old needs and new ends.