Ethereum’s Glamsterdam Upgrade Heads to Sepolia Testnet on October 6

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• Ethereum’s official roadmap lists “Sepolia fork, October 6, 2026” as the next milestone for the Glamsterdam network upgrade
• The Sepolia activation follows a round of devnet testing and moves Glamsterdam onto a public, permanent testnet ahead of any mainnet rollout
• Glamsterdam is the next major scheduled upgrade after Fusaka, continuing Ethereum’s practice of naming upgrades after the city hosting that cycle’s Devconnect event paired with a Beacon Chain-era city

The Ethereum Foundation’s own roadmap page, at ethereum.org/roadmap/glamsterdam, lists the next milestone for the network’s upcoming Glamsterdam upgrade as a “Sepolia fork, October 6, 2026,” moving the upgrade from internal devnet testing onto Ethereum’s public Sepolia testnet.

Sepolia is one of Ethereum’s longest-running public test networks and is used by application developers, infrastructure providers, and node operators to validate that their software works correctly against an upcoming protocol change before it reaches mainnet. Activating Glamsterdam on Sepolia gives the broader ecosystem, not just the core client teams that have been running devnets, a chance to test against the upgrade in an environment that more closely mirrors real-world conditions.

Glamsterdam follows Fusaka as the next major scheduled upgrade in Ethereum’s roadmap. Ethereum’s recent upgrades have generally been named by combining the city hosting that cycle’s Devconnect developer event with a city associated with the network’s Beacon Chain launch era, a naming convention the core developer community has continued with recent hard forks.

Moving to a public testnet is a standard, closely watched step in Ethereum’s upgrade process, sitting between private devnet testing, where core protocol teams iron out early bugs, and eventual mainnet activation, when the changes take effect for the live network carrying real economic value. A clean Sepolia fork with no major issues typically clears the way for a further public testnet activation and then a mainnet date; problems discovered at this stage can push mainnet timelines back while client teams address them.

Ethereum’s upgrade cadence has become more predictable in recent years as the core developer community has settled into a rhythm of shipping smaller, more frequent upgrades rather than infrequent, large ones. Glamsterdam’s specific mainnet date has not yet been finalized and will depend on how testing goes on Sepolia and any subsequent testnets, but the October 6 fork gives developers building on Ethereum a concrete near-term date to test their own infrastructure against.

Client teams and infrastructure providers typically treat a scheduled testnet fork like this one as the point where remaining implementation differences between execution and consensus clients need to be resolved, since discrepancies that surface on a public network with real, if worthless, test assets are easier to diagnose than ones that only show up once mainnet validators are staking real ETH. The roadmap page itself will be updated as further milestones, including any additional testnet activations and an eventual mainnet date, are confirmed by the core developers coordinating the upgrade.