Bitcoin mining difficulty rose 3.9% late Wednesday to hit a new all-time high in the final adjustment before the halving, estimated to occur on April 20.

The difficulty adjustment came at block height 838,656, reaching a record of 86.39 trillion, according to blockchain explorer Mempool. Bitcoin miners appear to be ramping up their hash rate in preparation for block subsidy rewards dropping from 6.25 BTC to 3.125 BTC next week.

Bitcoin mining difficulty measures how hard it is to mine a new block relative to the easiest it can ever be. It adjusts every 2016 blocks — roughly two weeks — to ensure that, on average, a new block is found every 10 minutes, regardless of how many miners are actively mining. The higher the difficulty, the more computational power and energy a miner needs to …