Ethereum's Holesky Testnet Shuts Down Ahead of Fusaka Upgrade

The Ethereum Foundation has announced the sunsetting of the Holesky testnet, a crucial platform for developers over the past two years. This closure comes as the network prepares for the upcoming "Fusaka" upgrade, signaling a transition in Ethereum's testing infrastructure. Developers are being directed to migrate to newer, supported testnets to ensure continued development and testing of protocol upgrades.

Key Takeaways

• Holesky testnet served developers for two years, facilitating the testing of numerous protocol upgrades.

• Critical downtime during Pectra testing in early 2025 highlighted smart contract address issues, necessitating infrastructure changes.

• Developers have a two-week window post-Fusaka launch in November to migrate from Holesky to alternative testnets like Hoodi and Sepolia.

Holesky's Two-Year Tenure and Purpose

Launched in September 2023, the Holesky testnet was designed to provide a secure environment for developers to implement and test new features and services on the Ethereum blockchain. Its primary function was to test staking infrastructure and validator operations at a large scale, successfully supporting thousands of validators in testing significant protocol upgrades, including the Dencun and Pectra upgrades.

Challenges and the Shift to New Testnets

During the testing phase for the Pectra upgrade in February and March 2025, Holesky experienced significant downtime. These issues stemmed from problems with specifying correct smart contract addresses for Pectra Request Hash Calculations, which led to post-launch disruptions and delays in finalization. These challenges underscored the need for improved testing frameworks and contributed to the launch of the Hoodi testnet in March.

The Ethereum Foundation is now guiding developers to transition all operations from Holesky to the Hoodi testnet, with the sunsetting process beginning on September 1. Following the Fusaka upgrade's launch in November, any remaining validator nodes on Holesky will have a two-week period to migrate to other supported testnets. After this period, Holesky will no longer receive support from client, testing, or infrastructure teams.

Future Testing Environments

Developers can now utilize several alternative testnets for their work. These include:

• Sepolia: A testbed for applications and tooling.

• Ephemery: A lightweight validator lifecycle testbed that resets every 28 days.

• Hoodi: The primary testing ground for developers moving forward.

This transition ensures that the Ethereum development ecosystem continues to benefit from robust and reliable testing environments as the network evolves.

Sources

• Ethereum Foundation Sunsets Holesky Testnet as Fusaka Upgrade Looms, Coinspeaker.