What is Ethereum Classic?
๐ New to this? Just start reading at the top โ it begins in plain English and gets more detailed as you scroll. Jump to any level:
๐ข The simple version
Plain English โ no jargon. Start here.
Ethereum Classic is the original Ethereum blockchain, preserved exactly as it was after a famous hack in 2016 โ the community chose not to reverse the hack, making it the original unaltered chain, while modern Ethereum is the forked version that did reverse it.
The DAO hack of 2016 โ why Ethereum split
In June 2016, a project called The DAO raised approximately $150 million in ETH from investors โ the largest crowdfunding in history at the time. The DAO was a smart contract that would let investors collectively vote on funding proposals. Three weeks after launch, an unknown attacker exploited a vulnerability in the code and drained approximately $60 million in ETH.
The Ethereum community faced an unprecedented question: should the blockchain be altered to reverse the theft and return the funds to investors? This would mean rewriting history โ something blockchains are theoretically not supposed to allow. It would violate the principle of "code is law" โ if the smart contract code allowed the exploit, some argued the attacker had technically done nothing wrong by the rules of the protocol.
The majority of the Ethereum community voted to perform a hard fork โ effectively reversing the hack and returning the funds. Most miners and users followed this new chain, which is what we today call Ethereum (ETH). A minority believed altering the blockchain was a dangerous precedent and continued mining the original, unaltered chain โ this became Ethereum Classic (ETC).
What Ethereum Classic stands for
ETC's community holds to a principle: "Code is Law." If a smart contract executes according to its code, that execution is final โ regardless of whether the outcome was intended. This principle makes ETC genuinely immutable โ no entity, no community vote, no developer team can ever reverse a transaction. The DAO hack funds remain on the ETC chain, moved by whoever holds those keys today.
ETC today โ what it is in practice
Ethereum Classic uses proof of work โ unlike Ethereum which switched to proof of stake in 2022. After Ethereum's Merge, some Ethereum miners who did not want to move to PoS migrated their equipment to ETC, temporarily increasing its hash rate. ETC maintains the same smart contract capabilities as early Ethereum, with EVM compatibility. It has a fixed maximum supply of approximately 210 million ETC โ unlike Ethereum, which has no hard cap.
Is it legal in India?
Yes. ETC is a VDA under Indian law. 30% tax and 1% TDS apply. See India regulation.
๐ก A bit more detail
For when you want to go a little deeper.
The fork in full โ technical and political
The fork occurred at Ethereum block 1,920,000 on 20 July 2016. The majority chain (ETH) implemented a hard fork that effectively moved The DAO's funds to a recovery contract, allowing original investors to withdraw their ETH at a fixed rate. The minority chain (ETC) rejected this intervention and continued from block 1,920,000 with the original, unaltered state โ including the attacker's drained funds.
This was not a technical accident. It was an explicit, contested governance decision. The community voted on Carbonvote.com (an unofficial but widely cited straw poll) โ approximately 87% of participating ETH supported the fork. Critics noted that voter turnout was low relative to total supply, and large holders dominated the vote.
ETC is used primarily as a store of value by holders who prefer its fixed supply and immutability philosophy. It is also used for smart contract deployment โ ETC has EVM compatibility, so Solidity contracts work on it. After Ethereum's Merge (September 2022), ETC became the largest GPU-mineable EVM-compatible chain, attracting miners who invested in GPU mining hardware. The ETC Cooperative maintains active development of the protocol.
51% attacks โ ETC's security challenge
ETC has suffered multiple documented 51% attacks โ where a single actor temporarily controlled more than half of the network's hash rate, allowing double-spend attacks. Documented attacks occurred in January 2019, August 2020 (three times in one month), and smaller attempts subsequently. These attacks are possible because ETC's hash rate is relatively small โ a sophisticated attacker can rent enough hash power to temporarily dominate the network.
In response, ETC implemented MESS (Modified Exponential Subjective Scoring) in 2020 โ a defence mechanism that makes deep chain reorganisations increasingly difficult by requiring exponentially more proof of work to rewrite older blocks. This has significantly reduced the practical attack surface.
Key ETC metrics: hash rate (security indicator โ higher is more secure), active addresses, DApp activity, and the premium or discount vs ETH (reflects market's assessment of the immutability thesis vs modern Ethereum's capabilities). Live data: CoinGecko ยท ETC Block Explorer.
๐ฃ The full technical picture
For the technically curious.
ETC's monetary policy โ fixed supply divergence from ETH
ETC implemented a fixed monetary policy in 2017 (ECIP-1017) that was not part of original Ethereum. The block reward decreases by 20% every 5 million blocks (the "Fifth-ing"). Initial reward was 5 ETC. After multiple reductions, the current reward is approximately 2.048 ETC per block. Maximum supply is capped at approximately 210.7 million ETC โ a deliberate echo of Bitcoin's scarcity model. This is a fundamental divergence from Ethereum's issuance model, which has no hard cap and adjusts issuance via governance.
Source: ECIP-1017. Ethereum Classic Improvement Proposal. ecips.ethereumclassic.org/ECIPs/ecip-1017
Thanos and Magneto upgrades โ Ethash to Etchash
ETC diverged from Ethereum's mining algorithm in November 2020 with the Thanos upgrade (ECIP-1099), which modified the DAG (Directed Acyclic Graph) growth rate for Ethash mining. The modification โ called Etchash โ was designed to keep the DAG size manageable for 4GB GPU miners who were unable to mine Ethereum's expanding DAG. This preserved GPU mining accessibility and attracted miners post-Merge. Subsequent upgrades (Magneto 2021, Mystique 2022, Spiral 2023) brought ETC's EVM closer to compatibility with Ethereum's mainnet changes.
MESS (Modified Exponential Subjective Scoring, implemented via ECIP-1100) assigns an exponentially increasing "score" to the current chain tip relative to alternatives. When a node receives a competing chain, the competing chain must have exponentially more total difficulty than the canonical chain to be accepted as the new tip for deeper reorgs. Specifically, the required difficulty advantage grows as 2^(reorg_depth). A 1-block reorg requires minimal extra work; a 100-block reorg requires 2^100 times the work of the canonical chain โ practically impossible. This asymmetric defence is effective against the deep-reorg double-spend attacks ETC suffered in 2020.
Key protocol parameters
- Consensus: Proof of Work (Etchash, GPU-mineable)
- Block time: ~13 seconds
- Max supply: ~210.7 million ETC (fixed, ECIP-1017)
- Current block reward: ~2.048 ETC (decreasing "Fifth-ing")
- Smart contracts: EVM-compatible (Solidity)
- Fork from Ethereum: Block 1,920,000 (July 2016)
- 51% defence: MESS (ECIP-1100, 2020)
- Key principle: Code is Law โ immutable chain
Source: ETC Cooperative. etccooperative.org ยท ECIPs: ecips.ethereumclassic.org