Seed phrase

The sequence of words, commonly twelve or twenty-four, that acts as the master backup for a self-custody wallet. Anyone holding it can restore the wallet and move its funds, from anywhere, without any other credential.

Definition

A seed phrase, also called a recovery phrase, is the human-readable form of the secret from which a wallet derives all of its private keys. It is not a password protecting an account. It is the account, in a form that can be typed into any compatible wallet on any device.

What follows from that

Possession is control, immediately and irreversibly. There is no second factor to stop someone who has the words, no device binding, and no way to change them: a compromised seed phrase cannot be rotated, only abandoned by moving everything to a new wallet.

And loss is final in the other direction. No provider holds a copy, so a phrase that is destroyed or forgotten takes the funds with it.

The rule that follows

Nothing legitimate ever asks for it. Not support, not a wallet update, not a verification step, not a site that says it needs to check your balance. Every request for a seed phrase is an attempt to take the wallet, without exception, and treating it as a rule rather than a judgement call is what keeps it useful under pressure.

Connecting a wallet to a DEX never involves the phrase. Signing a transaction never involves it either.

Storing it

Offline, written or stamped rather than typed, and in more than one physical place if the amount justifies it. A photograph, a note file, a password manager entry and a cloud backup all move the phrase onto an internet-connected device, which is the thing the offline copy exists to avoid.

Where you will run into it

Once, when a wallet is created, and once more if it ever needs restoring. Any other moment a seed phrase comes up is a warning sign.