On June 27, 2021, the Bitcoin network recorded its slowest daily average block time in history at approximately 23 minutes per block — more than double the target of 10 minutes. The unprecedented slowdown was the direct result of China’s aggressive crackdown on cryptocurrency mining, which had forced a mass exodus of mining operations and driven the network’s hashrate down by roughly 40% over the course of the month to just above 80 exahashes per second.
TL;DR
- Bitcoin network recorded its slowest-ever average daily block time of 23 minutes on June 27, 2021
- Network hashrate fell approximately 40% during June to roughly 80 EH/s as Chinese miners shut down or relocated
- China’s crackdown targeted provinces including Sichuan, Yunnan, Qinghai, and Inner Mongolia
- BIT Mining moved 320 mining machines to Kazakhstan as part of the broader mining diaspora
- Bitcoin and Ethereum mining revenues fell 43% and 53% respectively during June
- A historic 27.94% mining difficulty adjustment was approaching in early July to rebalance the network
The China Crackdown Intensifies
June 2021 marked a pivotal month for Bitcoin mining. What began as regulatory pressure in specific Chinese provinces quickly escalated into a coordinated nationwide campaign to eliminate cryptocurrency mining operations. Provincial authorities in Sichuan — one of the last remaining strongholds for Chinese Bitcoin mining due to its abundant cheap hydropower — ordered the shutdown of mining facilities, joining earlier crackdowns in Qinghai, Inner Mongolia, and Yunnan.
The scale of the disruption was enormous. China had been responsible for the majority of global Bitcoin hashrate, and the sudden loss of mining capacity sent shockwaves through the network. Bitcoin’s global average hashrate plummeted by approximately 40% over the month, falling from well over 100 EH/s to just above 80 EH/s. The immediate consequence was a dramatic increase in block times, as fewer miners meant less computational power available to process transactions and secure the network.
Miners Flee to Kazakhstan and Beyond
The crackdown triggered a geographic redistribution of Bitcoin mining that would reshape the industry for years to come. BIT Mining, one of the largest Chinese mining operators, announced that it had delivered 320 Bitcoin mining machines to Kazakhstan as part of its relocation strategy. The company indicated plans to move additional equipment in subsequent batches, joining a growing wave of Chinese miners seeking jurisdictions with favorable regulatory environments and affordable energy.
Kazakhstan emerged as an early beneficiary of the mining diaspora, offering proximity to China, relatively low electricity costs, and a government that was initially welcoming to cryptocurrency operations. Other popular destinations included the United States — particularly Texas with its deregulated energy market — as well as Canada, Russia, and various Central Asian nations. The migration would prove to be one of the most significant structural shifts in Bitcoin’s history, ultimately resulting in a more geographically distributed and resilient mining ecosystem.
Network Mechanics Under Stress
The 23-minute average block time recorded on June 27 represented the extreme end of the network’s stress response to the hashrate decline. Under normal conditions, Bitcoin’s difficulty adjustment mechanism — which retargets every 2,016 blocks, or approximately every two weeks — keeps block times close to the 10-minute target. However, the speed and magnitude of the hashrate drop meant that block times had become severely elevated before the next adjustment could take effect.
The network was approaching what would become the largest mining difficulty decrease in Bitcoin’s history: a 27.94% drop scheduled for early July. This adjustment would recalibrate the difficulty downward to match the reduced hashrate, bringing block times back toward the 10-minute target. Until then, users experienced slower transaction confirmations and temporarily higher fees as blocks took longer to mine.
Mining Revenues Collapse
The financial impact on miners was severe. Bitcoin mining revenues declined by approximately 43% during June, while Ethereum mining revenues fell by an even steeper 53%. The revenue decline was driven by a combination of lower cryptocurrency prices, reduced mining output due to the hashrate drop, and increased competition for the remaining blocks. Average network transaction fees also fell to yearly lows, further compressing miner income.
For Chinese miners who had not yet relocated, the situation was dire. Many were forced to sell mining equipment at steep discounts or abandon operations entirely. Those who managed to relocate faced significant capital expenditures for shipping, customs duties, and setting up new facilities in unfamiliar jurisdictions. Publicly traded mining companies were not immune either — Canaan (CAN), one of the leading mining hardware manufacturers, saw its shares decline 8% during the month.
Institutional Buyers Step In
Despite the mining turmoil, some institutional players viewed the market dislocation as an opportunity. MicroStrategy, led by CEO Michael Saylor, continued its aggressive Bitcoin acquisition strategy, purchasing an additional 13,005 BTC during June. The announcement helped lift MicroStrategy (MSTR) shares by 42% during the month, demonstrating that institutional conviction in Bitcoin remained strong even as the mining infrastructure underwent its most significant disruption to date.
Other crypto-adjacent equities also showed resilience. Coinbase (COIN) shares rose 6.8% during June, while Galaxy Digital (GLXY) gained 11.5%. The divergence between equity market sentiment and the underlying mining infrastructure challenges highlighted the growing sophistication of the cryptocurrency investment landscape.
Why This Matters
The events of June 27, 2021, represented a critical stress test for Bitcoin’s network architecture. The record-slow block times and dramatic hashrate decline demonstrated both the vulnerability of a concentrated mining ecosystem and the resilience of Bitcoin’s self-adjusting difficulty mechanism. The subsequent migration of mining operations away from China would prove to be one of the most significant decentralization events in Bitcoin’s history, ultimately strengthening the network against single-jurisdiction regulatory risk.
For the broader cryptocurrency market, the China mining crackdown of June 2021 served as a reminder that regulatory risk remains a potent force capable of disrupting even the most established blockchain networks. However, the market’s recovery — with Bitcoin and altcoins posting gains on June 27 despite the infrastructure challenges — also demonstrated the growing resilience of cryptocurrency as an asset class. Long-term investors continued to accumulate, on-chain indicators signaled oversold conditions, and the network’s fundamental design proved capable of weathering an unprecedented shock.
Disclaimer: This article is for informational purposes only and does not constitute financial advice. Past performance is not indicative of future results. Always conduct your own research before making investment decisions.
was mining in Sichuan when the orders came down. had 48 hours to shut down or lose equipment. relocated to Kazakhstan, then had to move again after the unrest in Jan 2022
BIT Mining moving 320 machines to Kazakhstan sounds tiny now but it was the start of a massive geographic shift in hashrate distribution
hashrate dropped 40% in a single month. miners losing 43% revenue on top of that. brutal summer for anyone running ASICs
the 27.94% difficulty adjustment was the largest downward adjustment in Bitcoin history at the time. network healed itself beautifully
23 minute blocks. try explaining that to a nocoiner who thinks btc is too slow already lmao