The supply limit is the maximum number of coins, which will be created. If a cryptocurrency does not have a supply limit, coin.Directory will not show this value.
The supply limit of Bitcoin (BTC)
It is defined within the Bitcoin algorithm that there will never be more than 21 million BTC. Currently there are 17 million BTC in existence and every day 1,800 new Bitcoins are issued. The issuance rate is cut in half every 4 years. Therefore in 2020 the daily issuance rate will drop to only 900 Bitcoins until finally in the year 2140 all 21 million BTC will be in existence and no new BTC are issued.
The following diagram shows the current supply of Bitcoin until 2140: