Mining Difficulty

What this measures

Mining difficulty expresses how hard it is to find a valid block. It is a multiple of the minimum difficulty, set at 1 when the network launched in 2009, and is shown here in T (tera, or trillions). Each point on the chart is one adjustment, as recorded by mempool.space. Unlike hashrate, difficulty is not an estimate: it is written into every block and checked by every node.

A reset every 2,016 blocks

Every 2,016 blocks, each node compares the time that actually elapsed with the 2-week target, that is 2,016 blocks of 10 minutes each. If blocks came in too fast, difficulty rises proportionally. If they lagged, it falls. A single adjustment cannot multiply or divide difficulty by more than 4, a safeguard against extreme swings.

The chart therefore draws steps rather than a smooth curve, and it reacts with a delay. If a large share of miners switches off, blocks slow down and the next adjustment takes longer than 2 weeks to arrive. A rise in difficulty also does not tell you whether new machines came online or older ones were swapped for more efficient models. It measures total power, not the number of miners.

A setting no one decides

This mechanism is what makes bitcoin issuance predictable. The block subsidy halves every 210,000 blocks, and difficulty keeps those blocks coming at close to 10 minutes. Because hashrate has almost always grown, blocks have on average arrived slightly faster than planned, and halvings a little earlier than the theoretical 4 years.

No central bank or foundation sets this parameter. It comes from a calculation every node runs on its own, and a block that does not meet the expected difficulty is simply rejected.

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The slow pace of adjustment is a choice, not a flaw. When Bitcoin Cash launched in 2017, its far more reactive emergency adjustment made hashpower oscillate between the two chains as profitability shifted, with blocks alternately very fast and very slow. For miners, every difficulty increase cuts what the same machine earns, which is what hashprice reflects.

Difficulty guarantees the pace of blocks, not the diversity of those who produce them. It would adjust in the same way to power spread across thousands of miners as to power coordinated by a few pools.