Passphrase

A passphrase, in the wallet context, is an optional extra word or sentence added on top of a seed phrase to derive a completely separate set of wallets. Under the BIP-39 standard it is sometimes called the 25th word: the same seed phrase combined with different passphrases produces entirely different addresses and balances, and there is no way to tell from the seed alone that a passphrase exists.

For example, a user might keep a small decoy balance on the wallet derived from the bare seed phrase, while their main savings sit behind the same seed plus a passphrase like a memorized sentence. Someone who steals the written seed phrase, or coerces the owner into revealing it, finds only the decoy. This makes passphrases useful protection against physical theft of a seed backup.

The danger mirrors the benefit: the passphrase is never stored by the device and cannot be recovered if forgotten. Because any string is valid, a typo silently opens a different, empty wallet rather than producing an error. A common misconception is that a wallet passphrase is like an account password that support can reset; it is a cryptographic input, and losing it means losing the funds behind it permanently, even with the seed phrase in hand.