This article was originally published by 8btc and written by Lylian Teng.

On September 16, 2019, BTC.com, Bitmain’s mining pool, lost its years’-long first place position to another China-based mining pool, Poolin, whose real-time hashrate read 13,378.00 PH/s at one point.

BTC.com, supported by the advantages of Bitmain’s bitcoin mining machines, has been the largest bitcoin mining pool for years. In the first half of 2018, the hashrate of mining pools under Bitmain (with BTC.com, AntPool and ViaBTC included) was approaching the dreaded 51 percent threshold needed to stage a 51 percent attack.

However, the bitcoin mining hashrate has become more decentralized as smaller pools made gains since the beginning of 2019. The rankings of mining pools saw a significant shift, particularly over the second half of the year, with Poolin moving to the second and even first place position at times.

Though BTC.com climbed back to its dominant position quickly, this upheaval shows that the bitcoin mining hashrate has been more distributed among the top mining pools and that the competition among these big pools is becoming fiercer.

Bitcoin hashrate distribution in 2013, 2018 and the year, respectively (Source: btc.com)

Founded in November 2017, Poolin’s rapid rise to the top mining pool spot may generate as much fear as admiration. Since the BTC mining pool went live in July 2018, its bitcoin hash power has been growing continuously. Apart from its increasing bitcoin hashrate, its hashrate for LTC and ZEC has steadily ranked first among global mining pools.

Poolin made headlines when its co-founders (CEO Zhibiao Pan, COO Fa Zhu and CTO Tianzhao Li) — three former employees of Bitmain who helped establish BTC.com — were sued by Bitmain for allegedly violating noncompete agreements.

As of press time, data shows that BTC.com’s hashrate has seen an increase of 0.37 percent in the past 24 hours, and that of Poolin’s has dropped by 2.99 percent, with the latter’s real-time hashrate reading 13,069.00 PH/s and BTC.com marking 13,560.00 PH/s. In terms of bitcoin hashrate distribution, BTC.com accounts for 18 percent in the past week, followed by Poolin with a share of 15.2 percent and China’s oldest bitcoin mining pool, F2Pool, ranking third at 13.8 percent.

Since its operation in late 2010, mining pools grow and shrink. According to incomplete statistics, nearly 20 pools that used to have big names have chosen to shut down, while China-based mining pools still dominate the market with a lion’s share of above 75 percent.