Term
Halving
A halving is a scheduled event in Bitcoin (and some other proof-of-work chains) where the block reward paid to miners is cut in half — occurring roughly every four years, this hard-coded scarcity mechanism caps Bitcoin's eventual supply at 21 million.
Bitcoin's block reward — the new BTC created per block and paid to the miner — is programmatically halved every 210,000 blocks (roughly every four years). It started at 50 BTC per block in 2009, dropped to 25 in 2012, 12.5 in 2016, 6.25 in 2020, and 3.125 in April 2024. This continues until roughly 2140, when the reward will effectively reach zero and 21 million BTC will have been mined in total.
The halving is Bitcoin's built-in disinflation mechanism. Because the issuance rate drops by 50% every four years, the annual supply growth slows over time — Bitcoin's "stock-to-flow" ratio approaches gold-like scarcity as halvings continue. Historically each halving has been followed by a bull cycle, though correlation is not causation and past cycles don't guarantee future ones.
After the last halving, miners will need to be paid entirely from transaction fees rather than block rewards. The economics of that transition are one of the long-standing open questions in Bitcoin — whether fee demand will be high enough to sustain the security budget.
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