Appendix A: Fork History

This appendix documents the major network upgrades (hard forks) for both Ethereum (ETH) and Ethereum Classic (ETC).

The DAO Fork and Chain Split

On July 20, 2016, at block 1,920,000, the Ethereum network experienced a contentious hard fork in response to The DAO hack:

• Ethereum (ETH) — Implemented the fork to return stolen funds
• Ethereum Classic (ETC) — Continued the original chain without the irregular state change

This split created two separate chains sharing a common history up to block 1,920,000.

Ethereum Classic Forks

Fork Name	Block	Date	Notable Changes
Frontier	0	Jul 2015	Genesis
Homestead	1,150,000	Mar 2016	EIP-2, EIP-7, EIP-8
DAO Fork	1,920,000	Jul 2016	ETC continues unforked
Tangerine Whistle	2,500,000	Oct 2016	Gas repricing
Spurious Dragon	8,772,000	Jan 2019	Replay protection
Atlantis	8,772,000	Sep 2019	Byzantium equivalence
Agharta	9,573,000	Jan 2020	Constantinople equivalence
Phoenix	10,500,839	Jun 2020	Istanbul equivalence
Thanos	11,700,000	Nov 2020	DAG size reduction
Magneto	13,189,133	Jul 2021	Berlin equivalence
Mystique	14,525,000	Feb 2022	London equivalence (no EIP-1559)
Spiral	19,250,000	Feb 2024	Shanghai equivalence (partial)

Ethereum Forks

Fork Name	Block	Date	Notable Changes
Frontier	0	Jul 2015	Genesis
Homestead	1,150,000	Mar 2016	EIP-2, EIP-7, EIP-8
DAO Fork	1,920,000	Jul 2016	Irregular state change
Tangerine Whistle	2,463,000	Oct 2016	Gas repricing
Spurious Dragon	2,675,000	Nov 2016	State clearing
Byzantium	4,370,000	Oct 2017	zkSNARK precompiles
Constantinople	7,280,000	Feb 2019	Cheaper gas, CREATE2
Istanbul	9,069,000	Dec 2019	Gas adjustments
Muir Glacier	9,200,000	Jan 2020	Difficulty bomb delay
Berlin	12,244,000	Apr 2021	Access lists (EIP-2929)
London	12,965,000	Aug 2021	EIP-1559 fee burn
Arrow Glacier	13,773,000	Dec 2021	Difficulty bomb delay
Gray Glacier	15,050,000	Jun 2022	Difficulty bomb delay
The Merge	15,537,394	Sep 2022	Transition to PoS
Shanghai	17,034,870	Apr 2023	Validator withdrawals
Dencun	19,426,587	Mar 2024	EIP-4844 blobs

Key Differences After The Merge

After September 2022, ETH and ETC diverged significantly:

Aspect	Ethereum (ETH)	Ethereum Classic (ETC)
Consensus	Proof of Stake	Proof of Work
Block time	12 seconds (fixed)	~13 seconds (variable)
Finality	~13 minutes (economic)	~10 minutes (probabilistic)
Monetary policy	Deflationary (burn)	Fixed emission schedule
Validator/Miner role	32 ETH stake	GPU mining

EIP Compatibility

ETC maintains EVM compatibility with ETH through coordinated upgrades:

ETH Fork	ETC Equivalent	Divergences
Byzantium	Atlantis	Full compatibility
Constantinople	Agharta	Full compatibility
Istanbul	Phoenix	Full compatibility
Berlin	Magneto	Full compatibility
London	Mystique	No EIP-1559 (fee burn)
Shanghai	Spiral	No withdrawals (not PoS)

ETC generally implements EVM-related EIPs while skipping consensus-related changes that assume Proof of Stake.

Resources

• ETC Forks: https://github.com/ethereumclassic/ECIPs
• ETH Forks: https://github.com/ethereum/EIPs
• ETC Block Explorer: https://blockscout.com/etc/mainnet
• ETH Block Explorer: https://etherscan.io