What is Circulating Supply
A fluctuating value that can rise and/or decrease over a time is the number of cryptocurrency coins or tokens circulating.
If a cryptocurrency is limited, new coins can progressively be created by mining. As in case of a central token, instantaneous minting can be used to increase the supply from developers at will.
The supply may also decrease: either deliberately through burning or through accidents, such as sending coins to an irreparable address or losing access to the wallet that stores money.
The network as a whole does not know reliably how much of the total supply is active and makes the circulation metric imperfect.
For example, although Bitcoin's current (BTC) supply should nominally be more than 18 million coins — as it is since the start of the network that many Bitcoin have been mined — it is estimated that about 4 million BTCs have been lost permanently, putting the real circulating supply closer to 14 million.
It is not necessary to confuse circulating supply with total supply, i.e. the number of mined coins until now, with less all deliberately burnt coins, or the maximum amount, which is the hard coded limit that neither total nor circulating supply can ever exceed.