xpub (extended public key)

An xpub is a wallet’s extended public key. It lets you derive all receiving addresses and watch the balance, but it can’t spend a single coin.

The BIP-32 standard describes how one key grows into a tree of child keys. An xpub is a public key together with a so-called chain code. From it you can derive further public keys and wallet addresses, but not private keys. It starts with “xpub”.

What’s it for? Creating watch-only wallets, for example in Sparrow: you see the balance and history, but you sign on a hardware wallet. In multisig, you exchange the xpubs of all participants to build the shared wallet.

An xpub doesn’t give access to funds, but it exposes the whole history and all future addresses. Whoever knows it sees your every move. The specification warns that knowing an xpub together with one child private key reveals the parent key. So treat it as confidential data.

Why it matters for your family

In a multi-signature wallet, the record of all keys’ xpubs is part of the backup. Without it, a family with two valid keys may not be able to rebuild the wallet. Where to keep it, and whether to add it to the instructions, is explained in the guide on 2-of-3 multisig.