The seed phrase is the most important key in the crypto world. With its 12 or 24 words, a wallet can be restored on any compatible device. If you lose it, you may lose access to your coins. If you reveal it, thieves can take them. This guide explains how a seed phrase works, why you should never translate it, how to store it properly and what to do if it is invalid or a word is missing.
Key facts at a glance
- A seed phrase (also called recovery phrase or mnemonic) usually consists of 12 or 24 English words from a list of 2,048 words.
- The wallet derives all private keys from it. The coins themselves are on the blockchain.
- Never translate your words into another language and write them down exactly as shown.
- The last word contains a checksum. A single missing or incorrect word can therefore often be reconstructed.
- Never enter your seed phrase on websites or in online tools, and never share it with so-called support staff.
What is a seed phrase?
A seed phrase is a sequence of words from which a crypto wallet derives all private keys and addresses. It is generated once when the wallet is set up and is then the complete backup: if your smartphone is lost or your hardware wallet breaks, you use the seed phrase to restore the same wallet on a new device, including all funds.
Depending on the wallet, it is also called a recovery phrase, mnemonic or secret recovery phrase (as in MetaMask). They all mean the same thing. Importantly, the seed phrase is not a password that can be reset. No one else knows it or can issue a new one.
How does a seed phrase work? The BIP39 standard
Most wallets follow the BIP39 standard, published for Bitcoin in 2013 and now also used for Ethereum and many other coins. The wallet generates a random number, appends a checksum and translates the result into words from a fixed list of 2,048 words. In the English list, the first four letters of each word are unique.
| Number of words | Random data | Checksum |
|---|---|---|
| 12 | 128 bits | 4 bits |
| 15 | 160 bits | 5 bits |
| 18 | 192 bits | 6 bits |
| 21 | 224 bits | 7 bits |
| 24 | 256 bits | 8 bits |
Because the checksum is contained in the last word, not every combination of words is valid. This is how a wallet detects typing errors and reports an invalid phrase. It is also why a single missing word can usually be narrowed down. You can read more about the word list itself in the article Seed phrase word list.
Seed phrase languages: why you should never translate it
BIP39 includes official word lists in ten languages: English, Spanish, French, Italian, Portuguese, Czech, Japanese, Korean and simplified and traditional Chinese. In practice, almost all wallets use the English list.
Two important rules follow from this: never translate your words into another language. And write them down exactly as the wallet displays them, in the correct order and spelling. A single translated or differently spelled word makes the phrase unusable for the wallet.
Seed phrase and wallet: not every phrase works everywhere
BIP39 is widespread, but not every wallet uses it in the same way:
- Ledger generates 24 words according to BIP39, MetaMask 12 words according to BIP39.
- Newer Trezor models create a 20-word backup according to the SLIP39 standard by default. These words come from a separate list and do not work in BIP39 wallets. More in the article SLIP39.
- Electrum uses its own seeds. They look like BIP39 phrases but are not compatible with them.
- Monero uses 25 words based on its own scheme.
BIP39 or SLIP39: the difference with Trezor
SLIP39 is a backup standard developed by SatoshiLabs, the maker of Trezor. It is based on Shamir’s secret sharing: the backup can be split into several shares, for example 5 shares of which any 3 are enough for recovery. Each share consists of 20 or 33 words from a separate list of 1,024 words. The drawback: only a few wallets support SLIP39, and a BIP39 wallet cannot do anything with it. Why I therefore usually recommend BIP39 is explained in the article SLIP39.
Even with genuine BIP39 phrases, wallets can differ in their so-called derivation paths. The same phrase then shows different addresses in another wallet, and the funds seem to be missing. You can read more about restoring individual wallets in the articles on MetaMask, Ledger and the Jaxx wallet.
How to store your seed phrase safely
The seed phrase is worth as much as the entire balance of the wallet. Store it accordingly:
- Offline: on paper or, better, on a metal plate that survives fire and water.
- Never digital: no photo, no cloud, no notes app, no email and no screenshot.
- A secure place: for example a safe or a bank safe deposit box. Keeping two copies in separate places protects you better against fire or loss.
- Store the passphrase separately if you use one (see below).
- Think of your heirs: decide how relatives can gain access in an emergency without revealing the phrase beforehand.
Anyone holding larger amounts should only let a hardware wallet generate the seed phrase. My comparison Best hardware wallet gives an overview, and more storage tips can be found in Cold storage: 5 effective secrets.
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The 25th word: the passphrase
Many wallets also offer an optional passphrase, often called the “25th word”. It is combined with the seed phrase and produces a completely different wallet. The tricky part: according to BIP39, every passphrase is valid. If you mistype or forget the passphrase, you get no error message, just an empty wallet.
A passphrase protects well against theft of the seed phrase, but it is also a common cause of loss. If you use one, store it separately from the seed phrase and document it just as carefully.
Seed phrase invalid or a word missing: what to do?
The wallet reports an “invalid phrase”
The most common causes are typos, an incorrectly copied word, swapped words, the wrong number of words or a phrase that was not created according to BIP39 at all, such as a SLIP39 or Electrum backup. First check whether all words are in the English word list and whether the wallet matches the type of your phrase.
One or more words are missing or illegible
If a single word is missing, this can be solved in most cases because the checksum greatly narrows down the possible candidates and a wallet with funds becomes visible on the blockchain. With several missing words or an unclear order, the effort increases considerably, but it is often still feasible. The key is not to rush and never to hand the phrase to strangers or enter it on websites.
The phrase is valid but the wallet is empty
This is usually due to a forgotten or wrong passphrase, a different derivation path in the new wallet or funds sitting on another network. In these cases the coins are generally not gone. How this relates to wrong networks is explained in the article Crypto sent over the wrong network.
Beware: seed phrase scams
Anyone who knows your seed phrase can empty your wallet within seconds. That is why many scams target exactly that:
- Online seed phrase generators and “validators”: phrases you generate or check there can be read by the operator.
- Fake support: no reputable wallet provider will ever ask for your seed phrase, whether by email, Telegram, X or Discord.
- Fake wallet apps and websites that ask for the phrase for “synchronisation” or “verification”.
- Shared seed phrases as bait: phrases with funds that were supposedly published by mistake but are actually a trap. More in the article Multisig scam.
More typical scams are described in the guide The 10 most common crypto scams.
A word is missing, the phrase is invalid or the wallet shows no funds? Before you try anything yourself, tell me about your case. The initial assessment is free, and you only pay if it succeeds. Get your case checked for free
Professional help with seed phrase recovery
If you are stuck, I can help. I am Ing. Thomas Jochen Wagner, MBA, and with Crypto Recovery I offer technical crypto recovery: incomplete or incorrect seed phrases, forgotten passphrases and wallet passwords, old wallets and crypto sent over the wrong network.
- Free initial assessment of your case.
- Your data stays with you: Recovery is usually done via Zoom. You carry out the steps yourself on your device under my guidance, or in person at my office in Perg (Upper Austria).
- Payment only on success: a flat fee of 100 euros for a recovered value below 1,000 US dollars, above that 10% of the recovered value. No upfront payment.
How the process works and how your data stays protected is described on the page Security & process. For a general overview, see the guide Wallet recovery. I cannot help with fraud, phishing or hacking. In that case, please contact the police. Get your case checked for free now.
Frequently asked questions about the seed phrase
What is a seed phrase?
A seed phrase is a sequence of usually 12 or 24 words from which a wallet generates all private keys and addresses. It is the backup of your wallet: anyone who knows the seed phrase can restore the wallet on any compatible device and control the funds.
Is there an official seed phrase in other languages?
BIP39 contains official word lists in ten languages, including Spanish, French, Italian and Japanese, but almost all wallets use the English list. Never translate your words into another language, otherwise the phrase will no longer match the wallet.
How do I store my seed phrase safely?
Offline on paper or, better, on a metal plate that survives fire and water, kept in a secure place. Never as a photo, in the cloud, in an online password manager or by email. Make sure your heirs know how to gain access in an emergency.
What if a word of my seed phrase is missing?
A single missing or incorrectly written word can be reconstructed in most cases because the last word contains a checksum. Never enter your phrase into online tools for this. Have the case checked by someone with whom the phrase stays on your own device.
Why is my wallet empty after the import?
Common reasons are a forgotten passphrase (25th word), a different derivation path in the new wallet or the wrong network. The funds are then usually still on the blockchain, just at addresses the new wallet does not display.
Is an online seed phrase generator safe?
No. A seed phrase generated on a website may be known to its operator. Always let your wallet generate the seed phrase itself, ideally a hardware wallet.
Sources: BIP39 specification, BIP39 word lists, SLIP39 specification.
