Unlike fiat currencies, which can be printed by central banks at their discretion, the supply of bitcoin is limited algorithmically.
Bitcoin’s (BTC) supply is finite. Once 21 million coins are generated, the network will stop producing more.
That is one of the main reasons Bitcoin is often referred to as “digital gold” — just like with the yellow metal, there is only a limited amount in the world, and someday, all of it will have been extracted.
As at 13 January 2020, there are just over 18 million Bitcoin in circulation, which is roughly 85% of the total cap — but it doesn’t mean that the cryptocurrency is about to reach its limit any time soon.