TL;DR
The master fingerprint is an 8-character code, such as a1b2c3d4, that identifies a seed (plus passphrase). It’s not secret. Use it to check that you connected the right device and unlocked the right wallet.
Where it comes from
It’s calculated from the master public key of your seed: the first four bytes of its hash, written as eight hexadecimal characters. The same seed and passphrase always give the same fingerprint; a different passphrase gives a completely different one.
Where you see it
- In Sparrow, in each keystore of your multisig.
- In your descriptor, in square brackets before each key.
- On the Ledger’s screen when you register the multisig.
What to use it for
- Write down the fingerprint of each device when you create the wallet (step 6)
- After replacing or restoring a device, check its fingerprint matches your notes
- Using a passphrase? A different fingerprint means you unlocked the wrong wallet
Is it private?
It reveals nothing that lets anyone spend. It can link wallets to the same device, so treat it like the descriptor: fine to store with your backups, no need to publish it.
It’s not the same as a two-vault check
The fingerprint stays the same for every account on the same seed, so it can’t tell your first vault from a second one. For that, look at the derivation path.