A seed phrase is the master backup of a wallet: 12 to 24 words that restore every key in it
A seed phrase, or recovery phrase, is a list of words from which a wallet generates all of its private keys. With it, the wallet can be restored on any compatible app or device, even without the original one. Anyone who has it controls the funds, no legitimate service will ever ask for it, and if it is lost, nobody can recover the wallet.
A group of easy-to-remember words used to generate a deterministic wallet (BIP-39). It backs up all private keys of the wallet and restores it on any compatible wallet, even without the original device (Ledger Academy).
Why are seed phrases 12 or 24 words?
Each word stands for 11 bits of a random number plus a short checksum. The standard allows 128 to 256 bits of randomness, in steps of 32, which gives five possible lengths.
- 2,048words in the BIP-39 wordlisttrezor.io
- 12 to 24words: 12, 15, 18, 21 or 24, set by the amount of randomnessgithub.com
- 25words in a Monero seed from the official wallet, the last one a checksumgetmonero.org
- 1 in 256random errors the BIP-39 checksum can missgithub.com
How does one phrase control a whole wallet?
- Randomness
The wallet picks 128 to 256 random bits and adds a checksum.
- Words
The bits are split into 11-bit groups, each pointing to one of 2,048 words.
- Seed
The words, plus an optional passphrase, produce the wallet's seed.
- Key tree
From that one seed, the wallet derives a whole tree of key pairs (BIP-32).
- Addresses
A standard path of five levels, purpose, coin, account, change and index, picks each address (BIP-44).
Is a seed phrase the same as a private key?
Seed phrase
- The master key for the whole wallet.
- Restores every account and address.
- Never share it, never type it into a website.
Private key
- Controls a single account.
- Derived from the seed.
- Never share it either.
Wallet password
- Only encrypts the wallet files on your device.
- Does not change the keys or the seed backup.
- Forgetting it is fixed by restoring from the seed.
What is the 25th word?
An optional passphrase is sometimes called the 25th word. Every passphrase produces a valid but different wallet, so only the right one opens the intended funds (BIP-39).
Heirs or anyone restoring the wallet need it as well as the seed phrase, and a lost passphrase cannot be recovered (Trezor).
How should I store my seed phrase?
A photo of the phrase is a safe backup.
Screenshots can sync to the cloud, and cloud theft is a common attack vector (ethereum.org).
Support may need my seed phrase to help.
No legitimate service will ask for your seed phrase or private key (ethereum.org).
The checksum will catch any typo.
The BIP-39 checksum misses about 1 in 256 random errors and cannot correct them.
I can recover a lost phrase through the wallet app.
The seed phrase is the only way to recover a self-custody wallet. Without it, access to the funds is lost (ethereum.org).
- Write it down and keep it offline. Ethereum.org advises not storing it on a computer.
- Keep the passphrase separate, if you use one, and make sure someone you trust knows how to find both.
- Check the words against the wallet's own backup check, one by one.
Seed phrases and swaps
A non-custodial swap sends from your wallet and delivers to your wallet, so your seed phrase is what protects both ends. Neither SimpleSwap nor ChangeNOW will ever ask for your private keys.
Questions
What is a seed phrase in crypto?
A list of 12 to 24 words from which a wallet generates all its private keys. It restores the wallet on any compatible app or device.
Is a seed phrase the same as a private key?
No. The seed phrase is the master key for the whole wallet. A private key controls a single account and is derived from the seed.
What happens if I lose my seed phrase?
If you still have access to the wallet, write down a new backup right away. If you lose both the phrase and the device, nobody can recover the funds.
Is it safe to store my seed phrase in a password manager or take a photo of it?
A photo or screenshot can sync to the cloud, and cloud theft is a common attack. Ethereum.org advises writing it down and not storing it on a computer.
What is the 25th word in a seed phrase?
An optional passphrase added to the seed phrase. Each passphrase opens a different wallet, and a lost passphrase cannot be recovered.
Why are seed phrases 12 or 24 words?
Each word encodes 11 bits. 128 bits of randomness plus a checksum makes 12 words, and 256 bits makes 24. BIP-39 also allows 15, 18 and 21.