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What is the difficulty adjustment?
The difficulty adjustment is Bitcoin's built-in rule that makes mining harder or easier so that blocks keep arriving about every ten minutes on average. Every 2,016 blocks, the network compares how long those blocks actually took with a two-week target and resets the difficulty.
What it means for you
Between adjustments, block times drift: if mining power joins or leaves, blocks come faster or slower than ten minutes until the next retarget, which changes how long you wait for confirmations. Since the subsidy schedule counts blocks, not days, events like halvings land earlier or later than a calendar estimate.
How it works
Every 2,016 blocks, nodes use the timestamps in block headers to measure how many seconds those 2,016 blocks took. The ideal is 1,209,600 seconds, two weeks. If they came faster, difficulty rises; if slower, it falls. One adjustment can raise difficulty by at most 300% or cut it by at most 75%. A valid block needs a header hash that does not exceed the target, so a harder target means more hashing attempts on average. The whitepaper describes this as a moving average aimed at a steady number of blocks per hour, compensating for faster hardware.
Sources: Bitcoin Developer Guide: Block Chain, Bitcoin: A Peer-to-Peer Electronic Cash System (whitepaper), Bitcoin FAQ (bitcoin.org) · checked 4 October 2026
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