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Bitcoin's Mining Difficulty Jumps 31.5 Percent, the Largest Single Increase Ever RecordedBitcoin's Mining Difficulty Jumps 31.5 Percent, the Largest Single Increase Ever Recorded

On July 9, 2011, Bitcoin's mining difficulty rose 31.5 percent in a single adjustment, the largest jump in Bitcoin's history. New miners were still piling in when this hit. The strange part: by the time it happened, the price rally that caused it had already collapsed.

How Difficulty Actually WorksHow Difficulty Actually Works

Bitcoin's difficulty adjusts roughly every two weeks, targeting an average block time of 10 minutes. More hashing power joining the network means blocks get found faster than that, so difficulty rises to compensate. It is a purely mechanical response to how much computing power is competing to mine.

The cause of the July 2011 spike traces back a month. Bitcoin's price had been climbing through early 2011 and spiked hard after a Gawker article on the Silk Road marketplace brought mainstream attention, peaking near $32 on June 8. Easy money brought a wave of new miners rushing to buy GPUs.

Satoshi himself had asked the community in 2009 to hold off on GPU mining, calling it a "gentleman's agreement," worried it would push out ordinary users running CPUs. That agreement did not survive contact with a price chart heading upward.

The Irony of the TimingThe Irony of the Timing

Here is what makes the record strange rather than simply large: those GPUs came online in late June and early July, after the price had already cracked. The June 19 Mt. Gox hack sent Bitcoin briefly to a penny before it recovered to single digits. Hashrate kept climbing anyway, hardware lagging weeks behind sentiment that had already reversed.

How It ComparesHow It Compares

This was not an isolated spike. All of 2010, Bitcoin's first year with a real market price, saw 32 difficulty increases out of 33 adjustments, averaging 22.85 percent, as early price discovery pulled in miners. July 2011 was that same pattern taken to its extreme.

2013 saw a similar dynamic on a larger scale. Two massive price rallies that year, one nearly twentyfold and one seventeenfold, drove 30 positive adjustments averaging 17.16 percent, while the industry simultaneously shifted from GPUs to dedicated ASIC chips.

A decade later almost to the month, the opposite extreme happened. China's 2021 mining ban forced more than half of global hashrate offline within weeks, triggering difficulty drops as steep as 27.9 percent, the mirror image of July 2011's spike.

The Record Still StandsThe Record Still Stands

Fifteen years, several bull markets, and an entire industry of mining farms later, the July 9, 2011 record for a single difficulty increase has never been broken. The biggest jump in Bitcoin's history happened while its first real price bubble was already bursting.

Part of an ongoing series on Bitcoin history. This event falls on July 9, 2011.