Xpub (Extended Public Key)

An xpub is a BIP 32 extended public key: a parent public key bundled together with its chaincode. With both pieces, anyone can derive all non-hardened child public keys (and therefore all addresses) under that branch of the wallet tree, without ever seeing a private key.

What you can do with someone's xpub:

• Watch their wallet. Import the xpub into Sparrow, Specter, BlueWallet, etc., and you'll see every receive address, every spend, every balance change in real time. No private key needed.
• Generate fresh receive addresses for them. A merchant server can hand out new addresses for each customer without holding any spending capability.
• Participate as a watch-only cosigner. Combine an xpub from each cosigner to build a multisig watching wallet.

What you give up by leaking an xpub:

• Privacy. Every present and future address in that branch is now visible to whoever has the xpub. The chain-analysis story collapses; the holder of the xpub sees the entire balance and transaction graph.
• Forward secrecy on activity. Even if you never share the xpub again, the holder can derive your next 1000 addresses just by walking the tree.

Treat an xpub like a balance sheet, not like an address.

Format variants you'll see in older wallets:

• xpub... - the original BIP 32 form, conventionally tied to legacy P2PKH derivations.
• ypub... - P2SH-wrapped SegWit (BIP 49).
• zpub... - native P2WPKH (BIP 84).
• Ypub / Zpub - multisig variants.

In 2026, the prefix variants are mostly historical: modern descriptor wallets carry the script-type information explicitly, so a single xpub plus a descriptor template covers everything cleanly.