Learn / Beginner · Using Crypto Safely

Seed phrases: the one rule

Beginner · Using Crypto Safely · about 5 min read

A seed phrase is a list of 12 to 24 words that can restore your wallet, and anyone who has it controls your crypto. The one rule: never share it.

How it works

• When you set up a self-custody wallet, it gives you a seed phrase, also called a recovery phrase. Ethereum’s guide says it is the only way to recover your wallet.
• Anyone who has the phrase can restore the wallet on their own device and move the funds.
• Crypto has no customer support to reverse a mistake, and transactions cannot be undone.

The one rule

• Never share it with anyone, ever. Do not type it into a website, a pop-up or a chat. Trust Wallet says it never asks for the phrase, so treat anyone claiming to be “support” who asks for it as a scammer.
• Do not store it on a computer or phone. Ethereum’s guide says not to store it on a computer, and Trust Wallet adds not to keep it in a screenshot or cloud note.
• Write it down and keep it offline. Paper or metal is the usual choice, with more than one copy in separate safe places.

Keep in mind

• If the phrase is lost and the device is lost too, there is no way to get the wallet back.
• If you keep coins on an exchange, you do not hold a seed phrase for them. The exchange holds the keys. See What is a crypto exchange?
• General information, not financial advice.

Where the phrase comes from

When you create a wallet, the app generates a long random number and then shows it to you as a list of ordinary words. Most wallets pick the words from a standard list of 2,048 so that the same phrase restores the same wallet in different apps. The words are only a readable form of the secret. From that one phrase, a wallet can recreate your private keys and every address that belongs to them, which is why one phrase can restore many accounts at once.

Phrase, password and PIN are different things

• A PIN or password usually protects the app on one device. Changing it does not change your funds or your phrase.
• The seed phrase works on any device, with no password. Whoever types it in owns the wallet.
• Resetting a password is not possible for a seed phrase, because no company holds it. That is the point of self-custody, and also its risk.

Storing it safely

Ethereum's guide says the phrase is the only way to recover a wallet and that it should not be kept on a computer. A few practical points follow from that:

• Write it by hand, in order, and check each word against the wallet screen. A single wrong or missing word can stop the restore.
• Keep more than one copy in separate places, so a fire, flood or theft in one place does not wipe you out.
• Paper works for a start. Metal plates resist fire and water, and several makers sell them.
• Never photograph it, type it into a notes app, or email it to yourself, because those copies can sync to the cloud or be copied from a stolen phone.
• Think about how a person you trust could find it if you were unable to, without leaving it where a stranger could.

Tricks aimed at your phrase

Scammers know the phrase is the whole prize. The usual tricks are a pop-up saying your wallet needs "validation", a fake wallet app or browser add-on that asks you to "import" your phrase, and a "support agent" who contacts you first. Ethereum's guide says legitimate services and support staff will not ask for it. If anything asks you to type the phrase into a website, close it. The only time you enter it is when you are restoring your own wallet inside the official app on a device you trust.

Common mistakes

• Believing an exchange account has a seed phrase you can lose. It does not, because the exchange holds the keys.
• Writing the phrase on a sticky note and leaving it next to the computer.
• Storing the only copy in the same place as the hardware wallet it restores.
• Splitting the phrase across places in a way you later cannot reassemble.
• Never testing the backup, then finding out it was written wrongly when it matters.

Try it yourself

Practise with an empty wallet so nothing is at risk.

1. Install a well-known wallet app from its official website or your phone's official store, not from a link someone sent you.
2. Create a new wallet and copy the phrase on paper, word by word.
3. Delete the app, install it again, and choose the option to restore from a phrase. Enter the words from your paper.
4. Check that the wallet address after restoring is the same as before. If it is, your backup works.
5. Then decide, while it still costs nothing, where the paper will live and who else could find it.

Key terms

Seed phrase, recovery phrase, self-custody, private key, offline.

Sources and credits

Recovery phrases and keeping them offline: ethereum.org, Wallets and ethereum.org, Stay safe. The standard 2,048-word list: BIP-39. General information, not financial advice.

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