Block 210,000 · 28 November 2012
The first halving
From its first day the software set a rule: every 210,000 blocks, about every four years, the reward for mining a block is cut in half. Block 210,000, mined on 28 November 2012, was the first to apply it. The miner who found it received 25 new bitcoins instead of 50, and so did every miner after, until the next halving.
The rule is what gives bitcoin a fixed supply. Each halving slows the creation of new coins, and the sum of all the rewards approaches 21 million without ever passing it. Nothing had to be decided or announced for it to happen: every node checks what every block pays its miner, and a block paying more than the new reward and its fees would simply have been refused.
The block holds 457 transactions, and its miner also collected their fees, which the halving does not touch. As the reward keeps shrinking, those fees are meant to become what pays for the security of the chain.
Three more halvings have followed, in 2016, 2020 and 2024, each at a height that is a multiple of 210,000. This one showed that the schedule written in 2009 would hold.