Seed phrase

Most wallets create all their keys from one random number, and show it to you as words so you can write it down. The words come from a fixed list of 2,048, set by a standard called BIP39, and the same words rebuild the same keys in any wallet that follows it. It’s also called a recovery phrase, a seed or a mnemonic.

That’s why, in a single-key wallet, everything depends on it. With it, you can restore the wallet on a new phone after losing the old one. Without it, a lost or broken device can mean the money is gone. And anyone who sees the words can take everything, from anywhere, without your phone or your password.

In practice

• Write it on paper or metal. A photo, a screenshot or a note in the cloud is a copy someone else may reach.
• No genuine app, exchange or support agent will ever ask for it. A request for it is an attempt to steal it.
• An optional extra word, the passphrase, turns the same words into a different wallet. It protects you if someone finds the words, but if you forget it, the words alone won’t get you in.

Some wallets never show a seed phrase. They back up the key to your phone’s cloud account, or spread control across several keys. That moves the risk rather than removing it: the account, or those keys, become what you protect.