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The block reward is halved every 210,000 blocks (or roughly every 4 years). In 2009, it was 50. In 2013, it was 25, in 2018 it was 12.5, and in May of 2020, it was halved to 6.25. Bitcoin successfully halved its mining reward—from 12.5 to 6.25—for the third time on May 11th, 2020.