Bitcoin Cash didn't launch in 2017: what a chain split actually creates
Ask when Bitcoin Cash was created and most sources answer 1 August 2017, "airdropped" to everyone who held bitcoin. That answer assumes one of the two chains is the original and the other a copy. The blockchain itself says something different: both chains run back to the same genesis block, and on that August day one chain became two.
When was Bitcoin Cash created?
Its chain begins with the genesis block of 3 January 2009, the same block BTC's chain begins with. The two share every block up to 478,558. On 1 August 2017 that one chain split into two branches running different rules: BCH and BTC. Everyone who held coins before the split held them on both branches afterwards, and every coin on either was mined.
What a split does to a ledger
A blockchain is its history: every block from the first, each one pointing to the one before. At block 478,559 two groups of nodes stopped agreeing on the rules. One group accepted blocks larger than one megabyte; the other did not. From that height each group built its own next block on the same shared history, and the chain had two branches.
Nothing was copied and nothing was created. Every unspent coin that existed at block 478,558 simply remained spendable on both branches, because both branches carry that history. Bitcoin Cash also added replay protection — a new signature rule, so that a transaction signed for one branch is not valid on the other — which is what let holders move their coins on each branch separately.
Why "airdropped to BTC holders" is an assumption
An airdrop is a distribution: someone with a supply of coins sends them to a list of addresses. Nobody sent anyone BCH. Holders kept the balances they already had, on both branches at once.
Calling it an airdrop to BTC holders treats BTC as the original chain and BCH as a new one that happened to copy its balances. The same arithmetic works in the other direction: every BCH holder "received" BTC. Which branch is the original is not something the chain can answer. Both have the same genesis block, the same pre-split history and the same claim to it. What one branch has is the ticker, the exchanges' default and the larger market — facts about the market, not about the chain.
What each branch changed after the split
| Change | BTC | BCH |
|---|---|---|
| Block size | 1 MB base limit kept; witness data outside it | 8 MB at the split, 32 MB from May 2018 |
| Segregated Witness | Activated 24 August 2017 | Not adopted |
| Replay protection | — | New signature rule (SIGHASH_FORKID) from the split |
| Replace-by-fee | Adopted | Not adopted |
| Later upgrades | Taproot (2021) | Schnorr signatures, contract opcodes, CashTokens (2023) |
Both kept SHA-256 proof of work, the ten-minute block target and the 21 million cap. Each branch then changed rules on its own, which is why the site counts them as separate cryptocurrencies — see why BTC, BCH and BSV are three cryptocurrencies.
The name and the original rules can part ways
Ethereum's 2016 split shows how little the name settles. After the DAO hack, most of the network adopted a rule change that moved the hacked funds; a minority kept running the rules as they had been. The branch that changed its rules kept the name Ethereum. The branch that kept the original rules became Ethereum Classic. If "original" meant the chain that kept the rules, Ethereum Classic would be the original; if it meant the chain that kept the name, it would be Ethereum. A split produces two branches, and which one people call the original is a choice.
How CoinSpectrum treats split coins
Each branch is its own cryptocurrency: its own chain and its own consensus. Neither is labelled a premine or an airdrop. The launch note on each asset page says the chains share their history to the split, and that nothing was allocated or sold: every coin was mined, before the split or after it. The same applies to Bitcoin SV, which split from Bitcoin Cash in November 2018, and to eCash, which split from it in November 2020.
Questions
Is Bitcoin Cash a fork of Bitcoin?
It is one of two branches of the same chain. Bitcoin Cash and BTC share every block from the 2009 genesis block to block 478,558; on 1 August 2017 the chain split and each branch continued under different rules.
Was Bitcoin Cash airdropped?
No one sent out BCH. Holders kept the coins they already had, on both branches, because both branches carry the same history. Calling it an airdrop to BTC holders assumes BTC is the original; the same arithmetic gives every BCH holder BTC.
When was Bitcoin Cash created?
Its chain starts with the genesis block of 3 January 2009. It became a separate branch on 1 August 2017, at block 478,559.
Which chain is the original Bitcoin?
The chain itself cannot say: both branches have the same genesis block and the same history up to the split. One has the ticker and the larger market; the other kept the original block-size path. "Original" is a label people choose, not a property of either chain.
Did Bitcoin Cash have a premine?
No. Nothing was allocated or sold at the split, and every coin on the chain was mined, either before the split or after it.