Glossary
Seed phrase
A seed phrase is a list of 12 to 24 words generated by a crypto wallet that encodes the master secret from which all its private keys are derived. It restores the wallet on any compatible device.
Also called Recovery phrase, Secret recovery phrase, Mnemonic phrase, Seed words, Backup phrase, BIP-39 phrase
See also
A seed phrase, also called a recovery phrase, is a sequence of ordinary words, usually 12 or 24, that a wallet shows you once when you create it. Those words are a human-readable form of the wallet’s master secret. From them, the wallet can regenerate every private key and address it will ever use.
How a seed phrase works
Most wallets follow BIP-39, a Bitcoin standard also used across Ethereum and many other chains. The wallet generates between 128 and 256 bits of randomness, adds a short checksum and splits the result into groups that each point to one word in a fixed list of 2,048 English words. That gives a phrase of 12, 15, 18, 21 or 24 words. The phrase is then turned into a seed, which feeds a key tree: one phrase, unlimited accounts and addresses.
BIP-39 also allows an optional passphrase, sometimes called the 25th word. Adding one creates a completely different set of wallets from the same words.
A concrete example
Nadia sets up a hardware wallet and writes the 24 words, in order, on the card supplied in the box. Two years later the device is lost. She buys a new one, chooses “restore”, types the 24 words and finds all her accounts, because the funds were always on the blockchain and the words recreate the keys.
Why it matters for users
The seed phrase is the master key to everything in the wallet. Whoever has the words has the money, on any device, anywhere in the world. Losing them without a backup means losing access for good. This is why it sits at the heart of self-custody.
Risks and good practice
- Write the phrase on paper or stamp it on metal; do not photograph it, store it in the cloud or email it to yourself.
- Keep it somewhere safe from fire, water and curious visitors; some people split copies across two locations.
- No legitimate wallet, exchange or support agent will ever ask for it. A website or message requesting your seed phrase is a scam.
- Check the words when you first write them down, in the right order and spelling.
Our guides Seed phrase security and How to avoid crypto scams go further.