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How are blockchain mainnet upgrades (hard forks) rolled out?

Published Sep 18, 2026Updated Sep 19, 2026Last verified Sep 18, 2026Requests recorded in this site’s own server logs, with the crawler identity checked by reverse DNS or IP range.Google9First collected Sep 19, 2026Recent requestsGoogleSep 20, 2026GoogleSep 20, 2026GoogleSep 20, 2026GoogleSep 20, 2026GoogleSep 19, 2026GoogleSep 19, 2026GoogleSep 19, 2026GoogleSep 19, 2026GoogleSep 19, 2026
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Quick answer

Proposed rule changes are written up as specifications, such as Ethereum Improvement Proposals, and implemented in every client. They are tested on public testnets, then activated at an agreed block or epoch so that all nodes switch together. On Ethereum, Pectra was rehearsed on testnets and activated on mainnet on 7 May 2025 at block 22,431,084. Fusaka followed on 3 December 2025.

62 words11 sources

Answer

Testnet problems during Pectra led to the launch of a new testnet, Hoodi, in March 2025 [11].

Sources

  1. officialNetworks — ethereum.org · accessed Sep 19, 2026 · Evidence page
  2. governmentIR 8202, Blockchain Technology Overview — National Institute of Standards and Technology (NIST) · accessed Sep 19, 2026 · Evidence page
  3. officialEthereum Launches — Ethereum Foundation Blog · accessed Sep 19, 2026 · Evidence page
  4. officialTimeline of all Ethereum forks (2014 to present) — ethereum.org · accessed Sep 19, 2026 · Evidence page
  5. officialApplication-Specific Blockchains — Cosmos Documentation · accessed Sep 19, 2026 · Evidence page
  6. officialCometBFT Documentation — Cosmos Documentation · accessed Sep 19, 2026 · Evidence page
  7. officialPrivate Networks — Go Ethereum (Geth) Documentation · accessed Sep 19, 2026 · Evidence page
  8. officialChain Operator Configurations — Optimism Docs · accessed Sep 19, 2026 · Evidence page
  9. officialClient diversity — ethereum.org · accessed Sep 19, 2026 · Evidence page
  10. officialEthereum Bug Bounty Program — ethereum.org · accessed Sep 19, 2026 · Evidence page
  11. officialHolesky and Hoodi Testnet Updates — Ethereum Foundation Blog · accessed Sep 19, 2026 · Evidence page