In-play supply (in-play BTC)

The bitcoin realistically able to change hands: mined supply minus provably lost coins, government-seized holdings, spot-ETF custody, and public-company treasuries. It is the headline number on the Galaxy Mind float tracker and the strictest practical answer to "how much bitcoin is actually left to buy."

Distinct from "circulating supply" (which counts lost and locked coins as circulating) and from exchange balances (which measure only custodial liquidity). In-play shrinks structurally: ETFs and treasuries absorb coins daily while mining issuance halves every four years.