How Bitcoin’s 21 million limit works
1. Hardcoded in software
The Bitcoin code says there will only ever be 21,000,000 BTC.
This rule is part of the consensus protocol that every Bitcoin node runs.
2. Enforced by the network
Every node checks new blocks. If a miner tries to create more than allowed, all other nodes reject that block as invalid.
3. No central authority can change it
To change the limit, you’d need a majority of miners, developers, exchanges, and users to agree and run the new code.
Given Bitcoin’s global, decentralized community, this is practically impossible without massive consensus.
4. Predictable issuance
New BTC are created only as mining rewards.
Rewards halve every ~4 years (the “halving” event), so the supply growth slows until it reaches zero around the year 2140.