Max supply

Max supply is the largest number of coins that will ever exist under a cryptocurrency's rules. Bitcoin's max supply is just under 21 million BTC, enforced by its halving schedule and checked by every full node.

Not every coin has a cap. Ethereum has no fixed maximum supply. Since 2021 part of every transaction fee is burned, so its supply can shrink during busy periods and grow when activity is low. Dogecoin adds a fixed 10,000 DOGE per block, about 5 billion new coins a year, with no cap. Stablecoins have no maximum supply because issuers create and redeem tokens as demand changes.

A hard cap alone does not make an asset valuable. What matters is demand relative to supply, and how credible the cap is. A cap set by a company or an upgradeable contract can be changed far more easily than one enforced by thousands of independent nodes.