The passphrase (the ‘25th word’): protection with side effects

The seed phrase is a master key: whoever finds it has access. With a passphrase, the words alone are no longer enough – but you gain a second secret that you have to back up just as carefully. We’ll explain calmly how it works – so you can decide for yourself whether you need one.

What the passphrase is

The BIP 39GlossaryBIP 39 (standard for seed words)The widely used standard that turns random data into 12 to 24 words from a fixed list of 2,048 words. Your wallet calculates all its keys from these words – BIP 39 is behind most seed phrases.On the learning path: Stage 5 · Step 3 – Backing up your seed phrase →In the glossary →× standard, which most wallets use to generate their seed phraseGlossarySeed phrase (recovery phrase)A sequence of usually 12 or 24 words from which your wallet derives all its private keys. Anyone who knows the words has full access to your bitcoin – so they belong in an offline backup and never in anyone else’s hands.On the learning path: Stage 5 · Step 3 – Backing up your seed phrase →In the glossary →×, provides for an optional extra field: the passphraseGlossaryPassphrase (the ‘25th word’)An extra word of your choice added to your seed phrase. The same words then produce a completely different wallet. This protects you if someone finds your words – but if you forget the passphrase, access is lost for good.On the learning path: Stage 5 · Step 3 – Backing up your seed phrase →In the glossary →×. It goes into the key calculation together with the words. If you don’t enter one, the wallet uses an empty string.^[1] That gives you your standard wallet.

The nickname ‘25th word’ is misleading: the passphrase doesn’t come from the word list, you choose it freely. TrezorProvider · Hardware walletTrezor SafeHardware wallets by SatoshiLabs from the Czech Republic – Safe 3, Safe 5 and Safe 7, each also as a Bitcoin-only edition.Hardware manufacturer – no financial licence required · reviewed Sept 2026Price: Safe 3: $59 · Safe 5: $129 · Safe 7: $249 (same amounts in euros, as of Sept 2026)On the learning path: Stage 6 · Step 1 – Hardware wallets compared →Our profile →AdVisit Trezor* (paid link, opens in a new window)on trezor.ioOnly buy hardware wallets from the manufacturer or an authorised reseller.*Paid link: if you sign up or buy through it, we earn a commission. Your price stays the same. How we make money →×, for example, allows up to 50 characters, and upper and lower case count.^[2]

The crucial point: every passphrase generates a valid wallet, but only the right one opens the wallet you want.^[1] There’s no error message. If you make a typo, you end up in a different, usually empty wallet.^[2]

The passphrases in the table are examples – never use them.

What it’s good for

Protection if someone finds your backup

This is the main reason: anyone who finds only your seed phrase – a burglar, a tradesperson, a flatmate – sees only the standard wallet. That’s why the Bitcoin Design Guide recommends a passphrase for larger amounts, kept separate from the seed phrase.^[3]

Camouflage: the decoy wallet

Because every passphrase opens a valid wallet, nobody can tell from the outside whether there are others – BIP 39 calls this ‘plausible deniability’.^[1] The decoy wallet builds on this: one wallet holds a smaller amount, while the larger balance sits behind a different passphrase. It’s meant for extortion under threat of violence, known as a wrench attackGlossaryWrench attack ($5 wrench attack)An attack using violence or threats instead of technology: criminals force Bitcoin owners to unlock their wallet or transfer bitcoin. The best protection is discretion – if nobody knows you own bitcoin, you are less likely to become a target.On the learning path: Stage 6 · Step 2 – Spotting scams →In the glossary →×. Jameson Lopp lists several hundred known cases of such attacks, and many more never become public.^[4]

Our assessment: a decoy wallet is a last resort, not a shield. It’s only convincing with a plausible amount and a genuine usage history, and anyone who knows the subject knows that passphrases exist. Better protection is not to draw attention to yourself as a bitcoin owner in the first place – more in Spotting & avoiding scams.

The risks

• Two secrets instead of one. If either is missing, the funds are gone – for heirs who don’t know about the passphrase, too.
• Weak passphrases can be guessed. Anyone who has your seed phrase can try passphrases automatically. Freely available tools do exactly that – they’re meant for recovering forgotten passphrases.^[5] A date of birth or a single word is therefore no protection.
• Typing on a computer. If you type the passphrase on a computer, malware can read along. Some hardware walletsTermHardware walletA small dedicated device that keeps your private keys offline and signs transactions internally.On the learning path: Stage 6 · Step 1 – Hardware wallets compared →In the glossary →AdManufacturers with a paid linkProviders from our comparisonBitBox02Hardware wallet · SwitzerlandVisit BitBox* (paid link, opens in a new window)Trezor SafeHardware wallet · Czech RepublicVisit Trezor* (paid link, opens in a new window)Blockstream JadeHardware wallet · Canada/USAVisit Blockstream Jade* (paid link, opens in a new window)All 6 compared – including non-partners →Only buy hardware wallets from the manufacturer or an authorised reseller.*Paid link: if you sign up or buy through it, we earn a commission. Your price stays the same. How we make money →× let you enter it directly on the device – with Trezor, for example, the Safe 3, Safe 5, Safe 7 and Model T.^[2]

What entering it on a hardware wallet looks like

The device is made up; the process on real models is similar.

The fingerprint is an eight-character short identifier, calculated from the wallet’s master public key (the first 32 bits of a hash).^[6] No keys can be derived from it, but it shows you straight away whether you’ve opened the right wallet. If your wallet doesn’t display it, use the first receiving address.

Choosing a good passphrase

• Nothing personal. Dates of birth, names, addresses or quotations can be deduced from your surroundings or appear in lists used for guessing.
• Several random words instead of a jumble of characters. Around four to six short, randomly chosen words joined with hyphens are hard to guess and easy to write down without errors. A short string such as X7!q is easily noted down wrongly and still isn’t secure.
• Simple characters. Not every device handles every character – Trezor, for example, only accepts ASCII, so no accented letters or ß.^[2] Lower-case letters, digits and hyphens cause the fewest problems.
• Don’t use it anywhere else, not even as a password for other services.

Come up with your passphrase yourself – not with online generators or websites.

If you’re choosing a new device, check with the manufacturer whether you can enter the passphrase directly on the device and which characters it accepts.

Backing up the passphrase

1. Write it down exactly

   Clearly distinguish upper- and lower-case letters, mark spaces, and write 0 and O, l and 1 so they can’t be confused. Trezor explicitly advises writing the passphrase down.^[2] Memory is not a backup.

2. Store it separately from the seed phrase

   If both are in the same place, the passphrase protects against nothing. Keep several copies of the passphrase, just like the seed phrase, but never next to a copy of the seed phrase.^[3] A seed backup never belongs on a digital device.^[7] Treat the passphrase the same way: no photo, no cloud, no password manager.

3. Note down an identifying feature

   Note the fingerprint or the first receiving address and keep the note with the passphrase or in the emergency letter, not with the seed phrase. Anyone who finds the seed phrase shouldn’t learn that there’s another wallet.

4. Test it regularly

   Trezor advises testing access regularly.^[2] Open the passphrase wallet about once a year and compare the fingerprint. The full test is explained in Testing recovery.

5. Mention it in your emergency plan

   Your heirs need to know that there’s a passphrase and where it is. The passphrase itself doesn’t belong in the emergency letter.^[3] How to set this up is explained in Inheritance & emergency plan.

Passphrase or multisig?

Both make sure that a single backup someone finds isn’t enough. MultisigGlossaryMultisig (multi-signature)A wallet in which several keys jointly control the bitcoin – for example 2 of 3. If one key is lost or stolen, the bitcoin stays safe. In return, setting it up and backing it up is considerably more demanding.On the learning path: Stage 6 · Step 4 – Inheritance & emergency plan →In the glossary →× with 2 of 3 keys also survives the loss of one key, but requires backups of all keys and of the wallet configuration.^[8]

More in Multisig simply explained.

Who is a passphrase worthwhile for?

When you’re starting out, a well-secured seed phrase is the better choice than a passphrase that nobody remembers later.

What’s next?