BTCC.

The BTCC pool was run by BTCC, a bitcoin exchange that began in Shanghai in 2011 as BTC China. BTC China announced the pool on 20 October 2014, and it found its first block, 326,351, the next day. At first its site was in Chinese only and all its miners were in China. It grew fast: within five weeks it had about 5% of Bitcoin’s mining power, and in 2016, its biggest year, it found about one block in eight. mempool.space credits it with 18,027 blocks in all. In October 2016 it was one of the few large pools to signal support for SegWitSegWitSegregated Witness: a 2017 upgrade that moved signatures into a separate part of each payment, making room for more payments., an upgrade to Bitcoin’s rules, as soon as miners could.

BTC China said at the launch that the pool shared each block’s reward in proportion to the work each miner had done, and in December 2014 that it paid a set amount for each piece of work instead, a method called pay per share. By 2016 it settled miners’ earnings every day. Most BTCC blocks paid the whole reward to one BTCC address in their first transaction, and the pool paid its miners from there. These are payments to the pool’s miners, separate from the transactions confirmed inside the block. BTCC also ran an exchange and a wallet, but a block found by its pool doesn’t mean the transactions inside it went through BTCC.

When China’s regulators pushed the country’s exchanges to close in September 2017, BTCC stopped trading in China, but its pool carried on. In January 2018 a Hong Kong blockchainBlockchainBitcoin's shared record of every payment since 2009, stored in blocks that each link to the one before — which is what makes it a chain. investment fund bought BTCC, and in June the pool provisionally agreed to sell 49% of its shares to Value Convergence Holdings, a Hong Kong financial firm; that November CoinDesk reported that it was unclear whether the sale had gone ahead. By then the pool had about 1% of Bitcoin’s mining power. Its last block, 543,040, was found on 25 September 2018. On 6 November BTCC said that, because of “business adjustments”, it would switch off the pool’s servers on 15 November and close it on 30 November.