What is a seed phrase?

Usually twelve or twenty-four words, a seed phrase deterministically derives a wallet’s keys. Anyone holding it holds the funds.

Why it matters

It is the single highest-value secret in self-custody and the target of nearly every crypto scam. No legitimate wallet, exchange, support agent, airdrop or recovery service will ever ask for it. Any request for it is theft, without exception. Store it physically, in more than one location, and never in a photo, a password manager note, a cloud document or an email to yourself. A phrase that exists only inside a burning house is as lost as one that was stolen, which is why the backup problem is a physical one.