What happens to lost Bitcoin?

Bitcoin that is “lost” refers to wallet owners that have lost access to their private keys.

Critics argue that this is a vulnerability of Bitcoin and cryptocurrencies. If users lose access to their wallets, there is no way to recover the funds. This forms part of a wider question on balancing the need for increased autonomy and privacy versus accessibility. There are private key custody services that users can use to keep record of their keys to prevent losses if they feel the service can be trusted to act faithfully.