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.
had miners in Sichuan that got shut down with zero notice. took 3 weeks to relocate machines to Kazakhstan. power grid there could barely handle the influx
watching the hashrate drop 40% in real time was surreal. Sichuan miners going dark overnight and the network just… slowed down but kept going
23 minute blocks. the network literally crawling and it still didnt break. say what you want about btc, the resilience is unmatched
23 minute blocks felt like watching the network gasp for air. difficulty adjustment kicked in exactly as designed and btc kept producing blocks. cant debasement this
watching my mining rigs sit idle for 6 weeks waiting for the difficulty adjustment was brutal. block 689472 took 23 minutes to mine. longest 23 min of my life
i was mining back then. watching hashrate drop 40% in weeks was terrifying. difficulty adjustment saved everything
Andrei P. was terrifying if you were mining. my S9 farm in Kazakhstan went from 20 sat/byte fees to basically printing money overnight once difficulty adjusted
block_clock_ kazakhstan mining was chaos. power grid couldnt handle the sudden influx of S9s. ISPs were clueless why bandwidth spiked overnight
the 27.94% difficulty adjustment that followed was the largest in history right? network self-healed in record time
27.94% was the largest downward adjustment ever. network hashrate recovered within 2 months as miners relocated to texas and kazakhstan
nonce_reveal_ 27.94% downward adjustment was the biggest ever at the time. miners relocating to Kazakhstan and Texas within weeks was chaos to watch
the difficulty adjustment kicking in after 2016 blocks was satoshis design working exactly as intended. beautiful to watch in real time
23 minute blocks and the network barely flinched. try doing that on any other chain and watch it grind to a halt
china banning mining was the best thing that happened to btc. network went from 60% chinese control to genuinely global distribution
glitchfix agreed. the ban forced geographic distribution overnight. painful short term but btc went from 60 percent China to genuinely global in 6 months
went from 60% concentrated in sichuan to hashrate spread across 60+ countries. the geographic resilience alone made the ban worth it long term
nodehorse 60% concentrated in sichuan to globally distributed in 12 months. china did more for bitcoin decentralization than any western policy ever did
nodehorse china banning mining forced decentralization faster than any protocol change could. ironic that authoritarian policy improved btc resilience
nodehorse the 60+ country redistribution is real but people forget most relocated miners ended up in just 3 countries. kazakhstan texas and canada absorbed 80% of the exodus
the 2016 block adjustment cycle wasnt designed for a 40% hashrate drop. satoshi assumed gradual miner churn, not a coordinated nation-state exit
23 minute blocks and the network didnt break. try that on solana and watch what happens
Hyun-woo K. the 27.94 percent difficulty adjustment that followed was the largest in history. network self healed in 6 weeks
sichuan_ghost the 27.94 percent adjustment was the self-correction working perfectly. satoshi designed it for gradual miner churn not a coordinated nation state ban and it STILL worked
sichuan_ghost_ the network self healed because difficulty adjusted. if satoshi had set a shorter window than 2016 blocks it wouldve been even faster. the design held up under a stress test nobody asked for
china banning mining accidentally decentralized bitcoin faster than any protocol upgrade could have. ironic
BIT Mining moved 320 rigs to Kazakhstan and people thought that was a big number. kazakhstan went from zero to 18 percent of global hashrate in six months
23 minute blocks and fees went parabolic. paid 800 sats/vB for a transaction that confirmed 3 blocks later. peak frustration