History of Ethereum Hard Forks

The Evolution of Ethereum Through Key Network Upgrades

Today marks a significant milestone for Ethereum—the mining of its 10 millionth block. This achievement represents over 15 zettahashes of computational power across five years. To put this into perspective, a high-end GPU like the GTX 1080 Ti would need 150 million years to match this output.

Throughout Ethereum's journey, several hard forks have shaped its development. While forks technically create chain splits, older chains are often abandoned, leading to what many call "network upgrades." Below, we explore each major fork that has defined Ethereum’s mainnet.

Pre-Launch: Olympic (Block #0)

On May 9, 2015, Ethereum introduced Olympic, a pre-release testnet serving as a proof-of-concept. It featured a bounty program rewarding participants with up to 25,000 ETH for stress-testing the network—such as sending the most transactions or identifying critical bugs.

Though Olympic was a separate network, it laid the groundwork for Ethereum’s Genesis block in the subsequent Frontier release.

Frontier (Block #0)

Frontier (Ethereum 1.0) marked Ethereum’s official launch. Its Genesis block allocated 72 million pre-mined ETH, including:

• 60 million ETH for presale buyers.
• 12 million ETH for the Ethereum development fund.

Key Features:

• Initial gas limit: 5,000 gas per block (only allowing empty blocks).
• "Thawing" period: Adjusted gas limits to 3.1 million after ~5 days.
• First transaction: Block #46,147 transferred 31,337 wei.

Ice Age (Block #200,000)

To enforce a future transition from Proof-of-Work (PoW) to Proof-of-Stake (PoS), Ethereum introduced an exponential difficulty increase. This "Ice Age" would eventually render mining impractical unless delayed by forks.

• Impact: Three visible spikes in block times (see chart in original).
• Purpose: Incentivize PoS adoption (though delays were frequent).

Homestead (Block #1,150,000)

Ethereum’s second major upgrade introduced three Ethereum Improvement Proposals (EIPs):

1. EIP 2: Adjusted gas costs and contract creation.
2. EIP 7: Added DELEGATECALL for modular contract interactions.
3. EIP 8: Ensured forward compatibility for network upgrades.

DAO Fork (Block #1,920,000)

In June 2016, a vulnerability in The DAO smart contract led to 3.6 million ETH being drained. The controversial EIP 779 proposed:

• Recovering funds: By modifying the attacker’s contract.
• Chain split: Opponents continued as Ethereum Classic (ETC).

Emergency Forks: Tangerine Whistle & Spurious Dragon

Tangerine Whistle (Block #2,463,000)

• Purpose: Mitigate DoS attacks via EIP 150, which repriced opcodes.

Spurious Dragon (Block #2,675,000)

• Key EIPs:

  • EIP 155: Replay attack protection.
  • EIP 160/170: Adjusted EXP costs and contract size limits.

Metropolis: Byzantium & Constantinople

Byzantium (Block #4,370,000)

• Notable changes:

  • Reduced block reward (3 ETH → 2 ETH).
  • Added opcodes (RETURNDATACOPY, STATICCALL).
  • Delayed Ice Age (again).

Constantinople/St. Petersburg (Block #7,280,000)

• Postponed due to EIP 1283 reentrancy risks.

• Finalized EIPs:

  • EIP 1014 (CREATE2 for deterministic addresses).
  • EIP 1234: Delayed Ice Age further.

Istanbul (Block #9,069,000) & Muir Glacier (Block #9,200,000)

Istanbul

• Highlights:

  • Gas cost adjustments (EIP 1884).
  • New precompiles (e.g., BLAKE2 hashing).

Muir Glacier

• Sole focus: Another Ice Age delay (EIP 2384).

FAQs

Why does Ethereum have so many forks?

Forks enable protocol upgrades, security patches, and feature enhancements while maintaining decentralization.

What’s the difference between a hard fork and soft fork?

• Hard fork: Requires all nodes to upgrade (e.g., DAO Fork).
• Soft fork: Backward-compatible (rare in Ethereum).

Is Ethereum Classic still active?

Yes, ETC persists as a PoW chain adhering to Ethereum’s original pre-DAO Fork rules.

👉 Explore Ethereum’s latest upgrades

👉 Dive deeper into DeFi innovations

References

• Ethereum Foundation Blog Posts (2015–2020).
• EIP Repository: eips.ethereum.org.

This structured evolution highlights Ethereum’s adaptability—from its experimental roots to a foundation for decentralized applications. Each fork reflects lessons learned and a commitment to scalability.