Ethereum's largest testnet Holesky to close after Fusaka fork
The Ethereum Foundation will shut down Holesky testnet two weeks after the Fusaka upgrade completes on the network. Developers must migrate their testing to three alternative networks: Hoodi, Sepolia, and Ephemery.
The shutdown follows Fusaka's planned testnet fork in the second half of September. After the two-week period ends, client teams, testing groups, and infrastructure providers will stop supporting Holesky. The mainnet Fusaka upgrade is scheduled for early November.
The Foundation said Holesky reached its planned end-of-life. The network launched in 2023 to test proof-of-stake operations at large scale. It handled rehearsals for major protocol upgrades including Dencun and Pectra.
Problems emerged after Pectra activated on Holesky. The network experienced extensive "inactivity leaks" that created long validator exit queues and slowed testing processes. These technical issues made it difficult to complete full lifecycle testing.
Hoodi will replace Holesky for most validator and staking tests. The network launched in March 2025 with a clean validator set designed to avoid Holesky's constraints. Sepolia will continue handling application and tooling work. Ephemery provides quick-reset validator cycles for specific testing needs.
Fusaka aims to improve rollup efficiency by spreading data availability workloads more evenly across validators. The upgrade should reduce costs and increase transaction speed for Layer-2 networks.
"After this, Holesky will no longer be supported by client, testing or infrastructure teams," the Ethereum Foundation stated.
Holesky became Ethereum's largest public testnet, supporting thousands of validators who tested upgrades before mainnet launches. Core development teams prepared the transition to the new testnet lineup as technical problems accumulated following Pectra's activation.
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