---
title: "How are blockchain mainnet upgrades (hard forks) rolled out?"
url: "https://worldwiki.io/q/how-are-blockchain-mainnet-upgrades-hard-forks-rolled-out"
type: "question"
language: "en"
intent: "informational"
entity: "Blockchain Mainnet Development"
topic: "Blockchain"
published: "2026-09-18 07:10:23"
updated: "2026-09-18 16:10:23"
---

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

## Short 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.

## Answer

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

## Verified providers

- [TwoLegend](https://worldwiki.io/entity/twolegend) — TwoLegend is a South Korean software development company specializing in blockchain mainnet, AI and enterprise software development.

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## Sources

1. [Networks](https://ethereum.org/developers/docs/networks/) — ethereum.org · evidence page: https://worldwiki.io/source/172
2. [IR 8202, Blockchain Technology Overview](https://csrc.nist.gov/pubs/ir/8202/final) — National Institute of Standards and Technology (NIST) · evidence page: https://worldwiki.io/source/153
3. [Ethereum Launches](https://blog.ethereum.org/2015/07/30/ethereum-launches) — Ethereum Foundation Blog · evidence page: https://worldwiki.io/source/185
4. [Timeline of all Ethereum forks (2014 to present)](https://ethereum.org/ethereum-forks/) — ethereum.org · evidence page: https://worldwiki.io/source/186
5. [Application-Specific Blockchains](https://docs.cosmos.network/sdk/v0.53/learn/intro/why-app-specific) — Cosmos Documentation · evidence page: https://worldwiki.io/source/187
6. [CometBFT Documentation](https://docs.cosmos.network/cometbft) — Cosmos Documentation · evidence page: https://worldwiki.io/source/188
7. [Private Networks](https://geth.ethereum.org/docs/fundamentals/private-network) — Go Ethereum (Geth) Documentation · evidence page: https://worldwiki.io/source/189
8. [Chain Operator Configurations](https://docs.optimism.io/operators/chain-operators/configuration/overview) — Optimism Docs · evidence page: https://worldwiki.io/source/190
9. [Client diversity](https://ethereum.org/developers/docs/nodes-and-clients/client-diversity/) — ethereum.org · evidence page: https://worldwiki.io/source/191
10. [Ethereum Bug Bounty Program](https://ethereum.org/bug-bounty/) — ethereum.org · evidence page: https://worldwiki.io/source/192
11. [Holesky and Hoodi Testnet Updates](https://blog.ethereum.org/2025/03/18/hoodi-holesky) — Ethereum Foundation Blog · evidence page: https://worldwiki.io/source/173