21 million cap

The 21 million cap is Bitcoin’s defining rule: the total number of bitcoin that will ever exist is fixed at just under 21 million. New coins are issued to miners on a schedule that halves every 210,000 blocks (roughly four years), tapering to zero around the year 2140.

The cap is not a promise from a company — it is enforced by every node independently rejecting any block that would break it. Changing it would require essentially all participants to opt into different rules, which is exactly what the system is designed to make impractical.