Bitcoin’s supply has a hard ceiling
Bitcoin’s rules limit the number of coins that can ever be created to 21 million. New bitcoins enter circulation as rewards for miners: computers that validate transactions and add them to the shared ledger. The reward shrinks by half after every 210,000 blocks, so new supply slows over time and eventually approaches zero.
That schedule makes Bitcoin different from ordinary national currencies, whose supply can expand when central banks issue more money. No single institution can decide to create extra bitcoins under the rules now used by the network. Changing the cap would require broad agreement among the people and businesses running Bitcoin software—not merely an order from a government or company.
The spendable supply may be smaller
The 21 million figure is a maximum, not a count of coins that will all be available to trade. Some bitcoins may be permanently inaccessible because their owners lost the keys needed to spend them. The ledger still counts those coins, but without the keys, nobody can move them. There is no reliable way to know exactly how many are lost.
Bitcoin can also be divided into tiny units, so a fixed number of whole coins does not mean transactions must be made only in whole coins. Divisibility makes the existing supply usable at many scales; it does not create more bitcoin.
Scarcity does not guarantee value
A fixed supply can make demand shifts matter sharply: if more people want bitcoin while the number available for sale is limited, buyers may bid up the price; if demand falls, the price can fall too. The cap therefore constrains supply, but it does not promise stability, purchasing power, or future demand.
As mining rewards diminish, miners are expected to rely increasingly on transaction fees paid by users. The striking consequence is that Bitcoin’s rules specify not only how scarce the asset can be, but also how the network must eventually pay to process transactions once new-coin rewards fade.
