A seed phrase is a list of 12 or 24 ordinary words that restores a crypto wallet. Whoever has the words controls the coins, on any device and in any country. That makes the seed phrase the most valuable thing you own in crypto, even more valuable than the wallet itself.
Below we explain what a crypto seed phrase is, how it works and what it looks like. We also cover the safest ways to store it and the scams built around it. If you are still choosing where to keep coins, first read our guide to the cold wallet.
Contents
- What a seed phrase is
- How a seed phrase works
- What a seed phrase looks like
- How to store a seed phrase safely
- How to recover a wallet
- Scams to watch out for
- Wallets without a seed phrase
- Frequently asked questions
What a seed phrase is
Coins never sit inside a wallet. Instead, they are records on the blockchain, and a private key proves which of them are yours. If this part is new to you, see how a blockchain records transfers.
The seed phrase is a human-readable backup of that key. In fact, from these words a wallet can recreate all of your keys and addresses. You may also see other names: recovery phrase, mnemonic phrase or secret recovery phrase. They all mean the same thing.
How a seed phrase works
When you create a self-custody wallet, the app generates a random number. It then turns that number into words from a fixed list of 2,048 English words, known as BIP39. As a result, 12 words carry 128 bits of randomness, and 24 words carry 256 bits. Guessing either one is practically impossible.
The last word also works as a checksum. Thanks to it, a wallet notices if you mistype a word during recovery. Moreover, the first four letters of every word on the list are unique, so one word cannot be confused with another.
Order matters as much as the words themselves. The same 12 words in a different order make a different wallet. Capital letters, on the other hand, do not matter, because the list contains only lowercase words.
Some wallets also offer an optional passphrase, sometimes called the 25th word. It adds a second secret on top of the seed phrase. However, if you forget the passphrase, the words alone will not bring the coins back.
What a seed phrase looks like
Here is a seed phrase example in the usual format. We made it up for this article, so never use it for a real wallet:
ocean, ladder, velvet, rescue, plastic, winter, normal, cable, orbit, gentle, harvest, tribe
A wallet shows the words only once, numbered, on its screen or in the app. After that, it asks you to confirm several of them. This way it makes sure you wrote them down correctly.
How to store a seed phrase safely
The best seed phrase storage is offline and physical. In other words, the words should never exist as a file, a photo or a message. These are the main options:
- Paper. It is free and simple, yet it burns, fades and gets wet. Write clearly and number the words.
- Metal plate. A steel or metal plate survives fire and water. You engrave or stamp the words, or place letter tiles into a frame.
- Two copies in two places. For example, keep one at home and one with a trusted relative. Then a single fire or burglary does not cost you everything.
Avoid anything connected to the internet: cloud storage, email, notes apps and screenshots. Likewise, never type the words into a computer to “save” them. After all, a seed phrase is only as safe as its weakest copy.
How to recover a wallet
You need the words only when the device is lost, broken or replaced. In that case, install the official app of a compatible wallet and choose “restore”. Then enter the words in the right order. The wallet recreates the same addresses, and your coins appear again, because they never left the blockchain.
Enter a seed phrase only in a wallet app or on a hardware wallet that you set up yourself. Never type it on a website, in a form or in a chat. Our step-by-step guide on how to create a crypto wallet shows how to set up a new wallet safely.
Scams to watch out for
Almost every attack on a seed phrase targets the person, not the technology. Watch out for these tricks:
- a “support agent” who asks for the words to verify or unlock your wallet;
- a website or app that offers to check the balance of a seed phrase;
- an online seed phrase generator that promises a “secure” phrase;
- a hardware wallet sold with a card that already has the words printed on it;
- a message about free coins that needs your phrase to claim them.
The rule is simple: anyone who asks for your seed phrase is a scammer. A genuine wallet creates the words itself, on your device, and never asks for them again.
Wallets without a seed phrase
Not every wallet uses words. Some hardware wallets back up the key on extra cards instead. For example, a Tangem wallet comes as a set of two or three cards, and each card can restore the wallet.
So if writing down words feels risky, a card backup is an alternative. Our overview of the best cold wallets compares wallets with and without a seed phrase.
Custodial wallets work differently again. The provider keeps the keys, and you log in with an email, a password and two-factor authentication. The SharPay crypto wallet works this way, so there is no seed phrase to lose.
Many people therefore combine the two. They keep savings under a seed phrase and spending money in a wallet with a virtual card you can top up with crypto.
Frequently asked questions
How many words are in a seed phrase? Usually 12 or 24, and some wallets use 18.
Can I change my seed phrase? Not for an existing wallet. Instead, create a new wallet with new words and move the coins there.
What if I lose my seed phrase? While the wallet still works, create a new one and move the coins right away. If both the device and the words are gone, nobody can restore access.
Is a seed phrase the same as a private key? No. A private key controls one address, while the seed phrase restores every key in the wallet.