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What is a seed phrase? The 12 or 24 words that control your crypto
A seed phrase, also called a recovery phrase, is a list of 12 to 24 ordinary words that a self-custody crypto wallet creates for you. The words back up the wallet’s master secret, so they can restore every account in it on a new device. Anyone who has your seed phrase can take your crypto, and nobody can reset it if you lose it. Write it down on paper or metal, keep it offline and never share it.
This guide explains how a seed phrase works, how to store it and how to spot the scams that target it. Still choosing a wallet? Start with our guide to cold and hot wallets.
What a seed phrase is
A seed phrase is also called a recovery phrase, a secret recovery phrase or a mnemonic.12 Under BIP-39, the common standard, the wallet generates 128 to 256 bits of random data, adds a short checksum and turns each group of 11 bits into one word from a fixed list of 2,048. So 12 words hold 128 random bits plus a 4-bit checksum, and 24 words hold 256 bits plus an 8-bit checksum.3
Because the last word includes the checksum, words picked at random usually do not form a valid phrase, and a wallet can catch many typos, though not all.3 BIP-39 also has word lists in other languages, but it strongly discourages them because the vast majority of wallets support only English, and a translated phrase creates a completely different wallet.3
What a seed phrase controls
A seed phrase is not the key to one coin or one address. The wallet turns the words into a seed,3 and from that single seed it derives a whole tree of key pairs.4 Under BIP-44, one seed can serve an unlimited number of coins, with several accounts per coin and millions of addresses,5 and an Ethereum address from your phrase works on every EVM-compatible blockchain.2 Two things follow:
- One backup restores everything. If your phone breaks or your hardware wallet is lost, the phrase restores the wallet, in most other wallet apps too.62
- One leak exposes everything. Ethereum.org calls the recovery phrase the master key to your wallet: anyone who has it can access all of your accounts and drain every asset.1
Seed phrase vs private key vs password vs PIN
These four secrets do different jobs:
| Seed phrase | Private key | Password | PIN | |
|---|---|---|---|---|
| What it is | 12 to 24 words that back up the whole wallet | A long code that controls one account | A secret you choose for an online account | A short code that unlocks one device or app |
| Can you change it? | No | No | Yes | Yes |
| If someone else gets it | They can take everything in the wallet | They can take the funds in that account | Not enough alone if two-factor authentication is on | They also need your device |
Private keys work like the recovery phrase, but for individual accounts,1 and a private key cannot be changed or replaced once created.6 Two-factor authentication ensures that a password alone is not enough to access an online account.1
Recovery phrase example: what a seed phrase looks like
A real seed phrase is just a numbered list of plain English words. The example below uses real BIP-39 words, but it is not a valid phrase: it fails the checksum, and the words say what it is.
| Example only: invalid, never use it | |||
|---|---|---|---|
| 1. sample | 2. phrase | 3. only | 4. never |
| 5. use | 6. this | 7. public | 8. example |
| 9. list | 10. danger | 11. empty | 12. void |
Never use a phrase you found online, got from someone else or received with a device: counterfeit hardware wallets are sometimes sold with a phrase the attacker already knows.7 Never invent your own either: BIP-39 is meant for computer-generated randomness.3
How to write down and store your seed phrase
- Write it by hand, in private. Set up the wallet where nobody can see your screen, and copy every word in order, exactly as shown.
- Never keep a digital copy. No photos, screenshots, notes apps, email or cloud files: screenshots can sync to the cloud, and taking keys from the cloud is a common attack.1 Any backup stored online is highly vulnerable to theft.8
- Use paper or metal. Paper can burn, fade or get wet; a metal plate resists fire and water better.
- Keep copies in more than one place. A backup that does not depend on a single location is less likely to be lost in one bad event.8 Each copy is a full key to your funds, so guard every one.
- Plan for your family. Your crypto can be lost forever if you have no backup plan for your family.8
The optional passphrase (the “25th word”)
Some wallets let you add a passphrase on top of the seed phrase, often called the “25th word”. BIP-39 combines the words and the passphrase to create the seed; without one, it uses an empty passphrase.3
The catch: every passphrase opens a valid wallet, but only the correct one opens yours.3 A typo shows no error, just a different, empty wallet, and a forgotten passphrase means lost funds. Keep it apart from the words, and use one only if you can look after both.
What to do if your seed phrase is lost or exposed
- Lost, but the wallet still opens. Act now: create a new wallet with a new phrase, back it up and move your funds there.
- Lost, and the device is gone too. The funds are almost always gone: it is often impossible to recover lost funds without the recovery phrase,2 and no one is likely to step in to help.9
- Seen by someone else. That includes a phrase typed into a website, photographed or saved in the cloud. Treat the wallet as compromised even if nothing is missing yet, and move everything to a new wallet on a device you trust.
After a theft, expect a second scam: people who promise to recover lost funds for an upfront fee. No legitimate firm offers guaranteed crypto recovery.7
The most common seed-phrase scams
Thieves rarely break the math; they trick you into handing the words over:
- Fake support agents. Scammers pose as wallet or exchange support, often after you post a question in public, and ask for your phrase to “verify” your account.7
- Fake “validate” or “sync your wallet” pages. A message links to an imitation website that asks for your seed phrase.1
- Fake wallet apps. Fakes can appear as sponsored search results or in app stores.7 Download a wallet only from its official website or app store.2
- Airdrop claims. Tokens or NFTs you never asked for come with a link to “claim” them; the site asks you to approve a transaction that can hand over your funds.1 Free money promises are always fake.9
Why a crypto exchange account has no seed phrase
Custodians such as crypto exchanges manage and control access to the private keys for you,6 and you sign in with a username and password that you can recover in the usual way.10 The trade-off is trust: if the custodian is hacked, shuts down or goes bankrupt, you may lose access to your crypto.6
Frequently asked questions
Is a seed phrase the same as a private key?
No. A private key controls one account. The seed phrase is the backup from which the wallet derives all of its keys.
Is a 12-word seed phrase less secure than a 24-word one?
Both are standard under BIP-39. Twenty-four words carry more random data, but for most people the bigger risk is a lost, photographed or shared phrase. Use the length your wallet creates.
Can I change my seed phrase?
No. Create a new wallet, write down its new phrase, move all your funds to it and stop using the old one.
What should I do if I lose my seed phrase?
If the wallet still opens, move your funds now to a new wallet with a new phrase. If the device is gone too, the funds are usually lost, and anyone who offers to recover them for a fee is likely a scammer.
Does a crypto exchange account have a seed phrase?
No. A custodial exchange holds the keys, and you protect the account with a password and two-factor authentication. A seed phrase becomes your job when you move crypto to a self-custody wallet.
Related guides: USDT networks explained · how crypto exchanges work
Risk warning. Crypto assets are volatile and carry risk. Crypto transactions are irreversible, and funds in a wallet whose seed phrase is lost or stolen may not be recoverable. This article is for educational purposes only and is not financial, investment or security advice.
Sources
- Ethereum.org, "Ethereum security and scam prevention." https://ethereum.org/security/ ↩
- Ethereum.org, "How to ‘create’ an Ethereum account." https://ethereum.org/guides/how-to-create-an-ethereum-account/ ↩
- Bitcoin Improvement Proposal 39 (BIP-39), "Mnemonic code for generating deterministic keys." https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki ↩
- Bitcoin Improvement Proposal 32 (BIP-32), "Hierarchical Deterministic Wallets." https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki ↩
- Bitcoin Improvement Proposal 44 (BIP-44), "Multi-Account Hierarchy for Deterministic Wallets." https://github.com/bitcoin/bips/blob/master/bip-0044.mediawiki ↩
- U.S. Securities and Exchange Commission, Office of Investor Education and Assistance, "Crypto Asset Custody Basics for Retail Investors – Investor Bulletin" (Dec. 12, 2025). https://www.investor.gov/introduction-investing/general-resources/news-alerts/alerts-bulletins/investor-bulletins/crypto-asset-custody-basics-retail-investors-investor-bulletin-0 ↩
- Bitcoin.org, "Avoid Scams." https://bitcoin.org/en/scams ↩
- Bitcoin.org, "Securing your wallet." https://bitcoin.org/en/secure-your-wallet ↩
- U.S. Federal Trade Commission, Consumer Advice, "What To Know About Cryptocurrency and Scams." https://consumer.ftc.gov/articles/what-know-about-cryptocurrency-scams ↩
- Ethereum.org, "Ethereum wallets explained: what is a crypto wallet?" https://ethereum.org/wallets/ ↩
This article is educational and is not financial, investment, or tax advice. Crypto assets are volatile and carry risk; do your own research and consider a licensed professional before making decisions. About our editorial process.
