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Last updated 2026-11-05

What Is a Passphrase?

A passphrase is an optional extra word that, combined with your recovery phrase, opens a different wallet. This page explains how that works, why it is not a second password, and the backup mistake that costs people their funds.

Who this is for

Anyone who saw a "passphrase" or "25th word" option while creating or restoring a wallet, and anyone considering one for a savings address.

What it is

Bitcoin Improvement Proposal 39, usually shortened to BIP39, defines how a recovery phrase of 12 or 24 words becomes a wallet. The standard includes an optional passphrase: any text you choose, mixed into the derivation alongside the words. Wallets that support the feature often call it the 25th word.

The result is a separate wallet. Your 12 words alone open wallet A. The same 12 words with the passphrase harbor-blue-2019 open wallet B, which has different addresses and, usually, an empty balance.

Nothing on the chain links the two. Restore the 12 words on a new device and enter no passphrase, and you will see wallet A only.

That is the trap. A wrong or missing passphrase does not produce an error. It produces a valid wallet with nothing in it, and the user concludes the funds are gone when they are sitting behind a string they did not write down.

Why it matters

The feature has two legitimate uses. It adds a layer that a phrase-only thief does not have: someone who finds your 12 words and restores them sees the empty wallet. And it creates a wallet that is not discoverable from the phrase, which some people use to keep a savings balance off the list of wallets a phrase reveals.

Both uses depend on one condition: the passphrase is backed up separately and exactly. Case, spaces, and punctuation are part of it. Store it with the recovery phrase and you have gained nothing, because anyone who finds one finds both.

Unlike a wallet password, there is no reset and no recovery. If the passphrase is lost, the wallet it opens is unreachable, and no support team can reconstruct it. If your wallet app does not offer the feature, you cannot add it to an existing wallet later; it applies when the wallet is created or restored.

Common misunderstandings

  • "It is a second password for the same wallet." It is not. It derives a different wallet, and the original stays reachable with the phrase alone.
  • "I can reset the passphrase if I forget it." There is no reset path. A forgotten passphrase means a lost wallet.
  • "Keeping it next to the recovery phrase is convenient." It also removes the protection, since one discovery exposes both.
  • "Any extra word will do." Derivation is exact. A typo opens a different, empty wallet rather than reporting a mistake.

Key takeaways

  • An optional BIP39 passphrase, often called the 25th word, creates a separate wallet.
  • It is not a second password and cannot be reset or recovered.
  • Losing it loses that wallet; the phrase alone opens a different one.
  • Back it up separately, never together with the recovery phrase.

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