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What is a BIP39 passphrase?
A BIP39 passphrase is an optional extra word or phrase added to a seed phrase. The seed phrase plus the passphrase together produce the wallet; the same seed phrase with a different passphrase, or none, produces a completely different wallet.
What it means for you
Every passphrase opens a valid wallet, so a typo gives no error: it shows an empty wallet instead of yours. Without the exact passphrase, including capitals and spaces, the funds cannot be recovered from the seed phrase alone. Someone who finds only your words cannot reach the passphrase wallet.
A common mistake: “The passphrase is just my wallet app's password.”
In fact: An app password only locks the app on one device. The BIP39 passphrase is part of the key itself: restoring the words anywhere without it opens a different wallet, and no app or company can recover it.
How it works
BIP-39 turns the words into the seed with PBKDF2, using the words as the password and 'mnemonic' plus the passphrase as the salt; with no passphrase, the salt is just 'mnemonic'. Any passphrase therefore produces a valid, different 512-bit seed, which the standard describes as plausible deniability. Nothing stored lets a wallet test a guess, so it cannot warn that a passphrase is wrong. Text is normalized to NFKD form first, but capitals, spaces and punctuation still change the result.
An example
Say you add the passphrase 'Harbor7' to your 24 words. Typing 'harbor7' opens a different, empty wallet, and so does 'Harbor7' with a trailing space. Each looks like a normal new wallet, so the only sign of the mistake is a zero balance.
Source: BIP-39: Mnemonic code for generating deterministic keys · checked 4 October 2026
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Educational content, not financial advice. Written by hand and checked against the source named above. Something wrong? Tell us and we reply within two business days.