Seed phrases: what they are and how to store them

A seed phrase (also called a recovery phrase or mnemonic) is a list of usually 12 or 24 words generated when you create a wallet. Most wallets follow a standard called BIP-39, which turns those words into the private keys for every account and every blockchain in the wallet.

That has one huge consequence: anyone who has the words has the wallet. They do not need your password, your device or your PIN. They can restore the wallet anywhere in the world and move everything out.

What a seed phrase is for

The phrase exists so you can recover your wallet if your phone or hardware wallet is lost, broken or stolen. That is its only job. In normal use you should never need to look at it, and you should almost never need to type it.

Where it should never go

• Into any website, including ones that look exactly like your wallet's site.
• Into a chat, email, form, "support ticket" or "validation" tool.
• Into a screenshot, a photo, cloud notes, a password-protected document or an email draft. Anything stored on an internet-connected device or cloud account can be stolen by malware or an account takeover.
• Into a "seed phrase checker" browser extension or app.

Danger: A page asking you to "enter your recovery phrase to verify eligibility", "sync your wallet" or "fix a pending transaction" is always a scam. No exceptions.

How to back it up properly

1. Write it on paper at the moment you create the wallet, in the order shown, and check every word against the screen.
2. Consider metal. Paper burns and fades. Stamped or engraved steel plates survive fire and water. They are worth it for larger amounts.
3. Store it somewhere private and stable: a home safe, a locked drawer, a bank safe deposit box. Not inside the hardware wallet box.
4. Think about two copies in two places so a single fire or flood does not wipe out both. More copies means more places it can be found, so balance this.
5. Test the backup. Some hardware wallets have a built-in "check recovery phrase" feature that verifies the words on the device itself without exposing them. Use that rather than restoring into a different app.

Passphrases (the "25th word")

Many wallets let you add an optional passphrase on top of the seed. It creates a completely separate set of accounts. Someone who finds your 24 words but not the passphrase sees only the accounts without it.

It is strong protection against physical theft, but it has a cost: if you forget the passphrase, those funds are gone forever. There is no reset. If you use one, store it separately from the seed and make sure someone you trust could find it if needed.

Mistakes that get seeds stolen

• Buying a hardware wallet from a reseller and finding a seed phrase already printed in the box. Real devices generate the seed themselves. A pre-filled card means the seller kept a copy.
• Typing the seed into a fake wallet app downloaded from a search ad or unofficial store listing.
• Storing it in a cloud photo library, a notes app or an email to yourself.
• Reading it out on a video call to "support".
• Splitting the words into halves across two places. That weakens it: each half dramatically reduces the work needed to guess the rest. If you want split backups, use a scheme designed for it, such as Shamir backup (SLIP-39) or multisig. See inheritance planning.

If you think your seed phrase was exposed

Treat the wallet as compromised even if nothing has happened yet. Some thieves wait for a larger balance. Create a new wallet with a new seed on a device you trust, move everything across, and stop using the old one. See I've been hacked.