Twenty-One Million

Twenty-One Million is an educational Bitcoin website with a public JSON Bitcoin halving API that calculates the halving era, block subsidy, and blocks until the next halving from a supplied block height.

API

What your agent can do

Give it a block height, get its halving era, block subsidy, and blocks until the next halving — as JSON.
Via API.

Tasks depend on the interface and permissions.

Connection methods

Choose a route that fits your agent.

API

For custom integrations

no account or key

Docs checkedView paths

API connection

API path

https://why21million.com/api/halving/850000

Authentication: No sign-in required.

Documentation

Documentation & experience

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Latest documentation check 10 Oct 2026

View sources and checks

API · Give it a block height, get its halving era, block subsidy, and blocks until the next halving — as JSON.Checked 10 Oct 2026

How documentation is checked

Twenty-One Million

What your agent can do

Give it a block height, get its halving era, block subsidy, and blocks until the next halving — as JSON.

Connection methods

API

Documentation & experience