In total, there will be just 21 million Bitcoin produced ever. The entire mining process will end in around 2140. Until then, the number of new coins that are created via the mining process will decrease by half, roughly every four years. This is known as the Bitcoin halving and was designed to create what economists call scarcity, therefore providing upwards pressure on prices.
While 21 million may sound like a very large number, when compared to the 8 billion or so people on earth, it is obviously incredibly small. It is this imbalance that leads many people to compare Bitcoin to gold and think of it as “hard” money.
As the first crypto to be created, the issuance process and schedule of Bitcoin has led the way for others. For example, Bitcoin Cash, Bitcoin SV and Zcash also have a hard cap of 21 million coins. Others, such as Litecoin, use the same framework but have a larger overall number.
However, there are coins whose schedule is very different. For example, both Dogecoin and Grin have issuance that is identical for every new block created forever, which means that their token supply is essentially unlimited. The founders of Grin hope that this feature will make it easier to maintain a stable price and thus become a more usable currency. It will take years to understand whether this actually happens.
In between these two positions are plenty of coins and a lot of tokens — many operating on Ethereum — that have a maximum issuance in place, but that number is very high. For example, Tron has a total supply capped at more than 100 billion.
There are also situations where the number of coins or tokens will reduce. Some projects have created rules in which a certain number will be burned — which means that they will be transferred into a wallet that cannot be recovered — at set intervals. Burning usually relates to operating fees, so that the more an asset is used, the faster its tokens are burned.