Bitcoin passphrase (25th word) explained
A passphrase is one optional extra secret: it protects you if someone finds your seed phrase, and it locks you out for good if you lose it.
A Bitcoin passphrase is an optional extra word or sentence you add to your seed phrase. Under the BIP39 standard, every passphrase opens a different wallet, so someone who finds your seed phrase without the passphrase sees an empty wallet. There is no "wrong passphrase" error and no reset: lose the passphrase and the bitcoin behind it is gone, even if you still have the seed phrase.
Disclosure: I work at Blockstream, the company that makes the Jade wallets mentioned here. I joined after many years as a satisfied user. There are no affiliate links on this site.
How the 25th word works
People call it the 25th word (or the 13th word with a 12-word seed) because it acts like one more word on the end of your seed phrase. It does not have to be a word: it can be any text you choose, and it is case-sensitive.
BIP39 turns your seed phrase into the master seed that every key comes from. It runs your words through a function called PBKDF2, 2,048 rounds of HMAC-SHA512, and mixes in the text "mnemonic" plus your passphrase. With no passphrase, the wallet uses an empty string. Change one character of the passphrase and the output is a different 512-bit seed, with different keys and different addresses.
As a result, no passphrase is invalid. BIP39 says every passphrase generates a valid seed, and only the correct one opens the wallet you want. A typo opens a new, empty wallet that looks normal, with no error.
Passphrase vs seed phrase
| Seed phrase | Passphrase | |
|---|---|---|
| Who creates it | Your wallet, or you with dice | You |
| Format | 12 or 24 words from the 2,048-word BIP39 list | Any text, case-sensitive |
| Typo protection | Checksum catches most typos | None. A typo opens a different wallet |
| What it does | Rebuilds the wallet | Selects which wallet the seed opens |
| Lose it | Restore from your backup | The passphrase wallet is gone for good |
You need both: a passphrase without the seed phrase is useless, and a seed phrase without the passphrase opens only the no-passphrase wallet.
Should you use a passphrase?
A passphrase protects you when someone gets your seed phrase backup. A burglar, a nosy relative, or a house sitter who finds the metal plate gets nothing without the passphrase, as long as the passphrase is stored somewhere else.
It also gives you a decoy. BIP39 notes that the scheme provides plausible deniability. Keep a small amount in the no-passphrase wallet and the real savings behind the passphrase, and someone who forces you to open the device sees a real wallet with real, smaller funds.
The cost is a second secret that can be lost. Losing it takes nothing dramatic: a forgotten capital letter, a backup that never got made, an heir who did not know a passphrase existed. Blockstream's own Jade guide says to use the feature only if you fully understand it, because it can greatly increase the risk of losing funds to user error.
My take: if your seed phrase backup is well hidden and you have a modest stack, skip it. If your stack is large enough that a found backup would change your life, use one, or move to multisig, which protects against a found backup without a secret you have to remember.
How strong a passphrase needs to be
Assume the worst case: someone has your seed phrase and is guessing the passphrase. They can try guesses on their own computer, with no lockout and no limit, as fast as their hardware runs. The 2,048 PBKDF2 rounds slow each guess, but they do not stop an attacker working through a list of likely passwords.
A passphrase from your life is weak. Your dog's name, your street, a favorite quote, or a password you use elsewhere are what an attacker tries first. Make it random, for example by rolling dice to pick words from the BIP39 list, the same way you would for a seed phrase. Each random word adds 11 bits, which multiplies the attacker's work by 2,048, so six random words give 66 bits. Use six or more.
Keep it typeable: you enter it on a small device screen every time you log in, and a passphrase that is painful to type is one you will eventually get wrong.
How to add a passphrase on Jade
I used Jade for years before joining Blockstream, so the steps below are for that device, from Blockstream's help center. SeedSigner also supports BIP39 passphrases.
- 1Before a wallet is active, open Options on the main menu and select BIP39 Passphrase.
- 2Choose how often Jade asks: Disabled, Next Login Only, or Always Ask. Next Login Only hides that you use a passphrase, because the prompt only appears when you turn it on.
- 3Choose the entry method. Manual gives you an on-screen keyboard with upper and lowercase letters, numbers, and symbols. WordList builds the passphrase from BIP39 words, written in lowercase with single spaces. Blockstream recommends Manual if you are unsure.
- 4Enter the passphrase and log in. Jade does not store the passphrase, so you enter it at every login that uses it.
- 5Write down the 8-character wallet fingerprint in the lower-right corner of the screen. Next time, if the fingerprint differs, you typed the passphrase wrong.
- 6Send a small amount to the passphrase wallet, log out, log back in with the passphrase, and confirm the fingerprint and balance match before sending more.
Backing up the passphrase
- Write it exactly, including capital letters, spaces, and symbols. "Satoshi" and "satoshi" are different wallets.
- Store it in a different place from the seed phrase. Keeping both together removes the protection the passphrase was supposed to add.
- Note the wallet fingerprint next to the passphrase. The fingerprint cannot spend anything, and it lets you confirm the right wallet opened.
- Make sure the person who would inherit your bitcoin knows a passphrase exists and where to find it. See my inheritance page.
The steps for the seed phrase itself are in my backup guide.
Lost passphrase: what recovery looks like
There is no reset: Jade does not store the passphrase, and no company holds a copy. Blockstream's help center states that if you forget the passphrase, you lose access to those funds permanently, even with the seed phrase.
If you remember most of it, there is a narrow path. btcrecover, an open-source tool on GitHub, can try variations of a BIP39 passphrase you partly remember. It works best when you have a reasonable idea of what the passphrase was, and it needs an address from the wallet (or a large address database) to check guesses against. It requires your seed phrase on a computer, so run it only on an offline machine, and treat any stranger offering to "recover" your passphrase as a scammer.
If you can still log in with the passphrase today but are not sure you could do it again, move the funds now to a fresh wallet with a backup you trust.
Frequently asked questions
What is the 25th word in a Bitcoin wallet?
It is the BIP39 passphrase: optional extra text added to a 24-word seed phrase (the 13th word with a 12-word seed). Each passphrase opens a different wallet from the same seed phrase.
Is a passphrase the same as a seed phrase?
No. The seed phrase is the 12 or 24 words your wallet gives you. The passphrase is extra text you choose, and it changes which wallet those words open. You need both to reach the passphrase wallet.
What happens if I enter the wrong passphrase?
You get a different, empty wallet with no error message. Check the wallet fingerprint your device shows. If it does not match the one you wrote down, re-enter the passphrase carefully.
What happens if I lose my passphrase?
The bitcoin in the passphrase wallet is gone. The seed phrase alone opens only the no-passphrase wallet. If you remember part of the passphrase, a tool like btcrecover, run offline, may be able to search the variations.
Can a Bitcoin passphrase be brute-forced?
A weak one can, if the attacker has your seed phrase, because they can test guesses offline with no limit. Make it random: six words picked with dice give 66 bits, and every extra word multiplies the guessing work by 2,048.