Halving

The halving is a scheduled event in Bitcoin's protocol that cuts the block reward — the amount of new bitcoin issued to miners with each block — in half, occurring every 210,000 blocks, roughly every four years. It is the mechanism enforcing Bitcoin's fixed 21 million supply: issuance started at 50 BTC per block in 2009 and has halved repeatedly — to 25, then 12.5, then 6.25, then 3.125 BTC in April 2024 — continuing until the final fraction is mined around 2140.

Halvings matter economically because they cut the flow of new supply while demand is unaffected, and they matter culturally because past halvings (2012, 2016, 2020, 2024) have each preceded major bull markets, giving rise to the popular "four-year cycle" theory. For example, the May 2020 halving reduced daily new issuance from about 1,800 BTC to about 900 BTC, and bitcoin's price rose severalfold over the following year — though how much the halving itself caused that, versus broader conditions, remains genuinely debated.

A common misconception is that halvings mechanically guarantee a price rally; each halving's supply effect is smaller than the last relative to existing supply, the event is publicly known years in advance and arguably priced in, and correlation with past bull runs is not proof of causation. Halvings also squeeze miner revenue, historically forcing less efficient operations to shut down. Other cryptocurrencies, such as Litecoin, have similar halving schedules, but "the halving" without qualification means Bitcoin's.