Recovering Your Mnemonic Phrase When You're Missing a Word (11 of 12 or 23 of 24 words)

Published on
December 22, 2023
Recovering Your Mnemonic Phrase When You're Missing a Word (11 of 12 or 23 of 24 words)
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Here's a very common scenario: someone goes to log into their crypto wallet, and they realize that they no longer know the password to their wallet.

  • Perhaps they upgraded to a new phone, and their old phone just remembered the password for them.
  • Perhaps they haven't logged into the wallet for a year, and they threw away the scrap of paper where their password was written.

Either way, they don't panic -- because they know that they wrote down their mnemonic phrase. And, with that phrase you can recover your wallet at any time.

But, when they type in all the words that they wrote down, they realize that they're missing one word: they have either 11 of 12 words or 23 of 24 words. Crisis! That final word is absolutely critical to recovering the wallet.

If you're in that situation, we can almost certainly help you recover your wallet. If you'd like professional help, contact us.

Understanding the Seed Phrase

These mnemonic phrases go by a lot of different terms: seed phrase, recovery seed, recovery phrase, 24 word phrase, mnemonic code -- all of these relate to the same thing: a series of words, randomly selected, that are used to generate the private key that controls your wallet.

As much as you might consider it impossible to remember these random seeming words, they were actually designed as a simpler way to remember your private key. Consider that previous to these recovery seeds you would have needed to remember a 52 character random string where each character could take 1 of 58 different values!

Despite its odd nature, this mnemonic sentence forms the cornerstone of your crypto world. Sure, you could use that 52 character Base58 string -- but who wants to remember a string of gibberish when you can have a phrase that you can jot down or even say over the phone?

Which Wallets use Seed Phrases?

With a few exceptions, pretty much every modern self-custody wallet since the 2015 / 2016 timeframe uses BIP39 recovery seeds.

This is true whether your wallet is a hybrid online wallet (like, a smartphone wallet (like Coinbase Defi wallet or TrustWallet), or a desktop or laptop wallet based in Chrome or in a standalone executable app.

The largest set of exceptions is the Bitcoin core wallet (also known as Bitcoin Qt), and the wallets derived from it (Dogecoin core, Litecoin core, etc). All of these wallets generate hierarchical deterministic private keys (BIP32) but they don't use BIP39 seed phrases. This isn't a super-important detail -- but, just know that if you are using Litecoin core in 2022, you aren't going to have a BIP39 seed phrase that you can use as a backup. (Your wallet.dat file is your wallet backup instead).

The IoPay wallet apparently gives you a private key as a backup, instead of a seed phrase.

Update, Jan 31, 2024: I have also discovered that the Argent wallet is a self-custody wallet that uses a different backup mechanism than a seed phrase.

Which Blockchains use Seed Phrases?

It doesn't matter if you have Bitcoin, Ethereum, Solana, Dogecoin, or the latest memecoin -- every blockchain uses BIP39 seed phrases.

To say that differently, if you are using a modern wallet the private key that controls your tokens was generated using a BIP39 seed phrase.

Again, you might be using the Bitcoin core wallet, and in that case you wouldn't have a BIP39 seed phrase -- but, if you're using a modern wallet that isn't Bitcoin core, you'll have a recovery seed.

How Big of a Problem are Missing Words?

An incomplete recovery phrase cannot recover your wallet, period, full-stop.

You have to find the missing words -- in the correct order -- if you're going to use the phrase to recover your private key.

Most people's initial reaction when they realize that they have a word missing is that they're probably missing the last word. We have even had clients that manually tried every word in the 2,048 word BIP39 dictionary in that last position.

However, while this may seem like a reasonable idea, if you try it you will soon realize that:

  • This is a long, boring and potentially mistake-ridden process;
  • There's no guarantee that the missing word is in the last position -- it could be in the 3rd position, or the 7th position or the 22nd position (in a 24-word seed phrase).
  • You not only have to regenerate the 12 or 24-word phrase for each of the 2,048 words in the dictionary, but you also have to check the first few addresses that were generated for each valid phrase to see if they have had a transaction.

Another serious problem with trying to find a missing word by hand is that it's possible that the partial recovery seed that you have is for the wrong wallet -- perhaps a wallet that's never had a transaction. That means that if you went through this process by hand, you could actually reconstruct the exact correct mnemonic phrase but you wouldn't know it -- because the wallet has never had a transaction.

Common Error Messages When You Have an Incomplete Mnemonic Phrase:

  • Blockchain: Invalid phrase
  • Coinbase defi: Enter a valid 12-word recovery phrase.
  • Electrum: BIP39 (checksum: failed)
  • Exodus: won't let you import the wallet with a partial phrase -- but, doesn't give you an error message.
  • Ledger: Invalid recovery phrase
  • Metamask: Secret Recovery Phrases contain 12, 15, 18, 21, or 24 words
  • Phantom: won't let you import the wallet with a partial phrase -- but, doesn't give you an error message.
  • Trezor: Recovery failed. Error details: Mnemonic is not valid
  • Trust Wallet: Secret Phrases must contain 12 or 24 words

How to Recover Your 12th or 24th Word by Hand

Practically speaking, to recover a missing word in your seed phrase you need to use software. However, you can learn a lot about how these mnemonics work by trying to recover one by hand.

There are 2,048 words in the BIP39 dictionary, and there are 12 possible positions that that word can be placed (for a 12 word recovery seed) and 24 possible positions for a 24 word recovery phrase.

The basic process of finding the right missing word can be described as "brute forcing" the word.  

You take your 11-word phrase and you place the first of the 2,048 words in position 1, followed by the remaining 11 words. You then check to see whether the 12th word is a valid checksum -- only 128 words can be a valid checksum for any given phrase in that 12th position.

If it generates a valid checksum, you need to derive the first few addresses that would be generated by that 12 word phrase, and see whether any of those addresses have ever had a transaction. If they have, then you have found the correct seed phrase! If they haven't, then you likely haven't found the correct seed phrase.

Assuming that you did not find the correct seed phrase, you would now place the 2nd of the 2,048 words in the first position and repeat the process until you either find the correct word in the correct position, or exhaust the list of possibilities.

And, to be clear, there are 12 x 2,048 = 24,576 possible combinations for a 12 word seed phrase, and 24 x 2,048 = 49,152 possible combinations for a 24 word seed phrase.

On tool to try this by hand is Ian Coleman's BIP39 tool. For example, let's imagine that the correct seed phrase is: outside risk fluid inform fluid motion ice web exact small mixed usual

But, we've lost a word somewhere in the phrase, and all we have recorded is: outside risk fluid inform motion ice web exact small mixed usual

So, we could open the BIP39 tool in one browser tab, and the BIP39 English dictionary in another, and try the first combination, which is:

abandon outside risk fluid inform motion ice web exact small mixed usual

The BIP39 tool quickly gives us the message "Invalid mnemonic"

We can now continue with that process until we find a first word that is a valid mnemonic.  (In this case, it's the 29th word, "adjust"):

The next step depends on whether you know your Bitcoin (or other crypto) address or not -- if you know it, you can search for it on the BIP39 tool (under "Derived Addresses").  If the address is there, you have found the correct recovery seed! If the address is not there, you have to keep looking.

Alternately, if you don't know the address where your funds are stored, you can enter the first 5 or so addresses listed under "Derived Addresses" in a blockchain explorer, like, to see if they have ever had a transaction.

If they have ever had a transaction, then this is likely your correct recovery phrase.

If you reflect on this process for more than a couple of seconds, you'll realize that it's not really possible to do this by hand.

If you have a technical background and you're comfortable working on the command line of your operating system, you could install a piece of software called seedrecover, and use that to try to brute force your mnemonic phrase.

On the other hand, if you're not confident in your technical skills, please contact us and we'll resolve this problem with you.

What if you're missing more than 1 word?

All of the same problems exist if you're missing more than 1 word that you have if you're missing 2 or more words: you don't know which word is missing, and you don't know in which position the word is missing.

It's relatively easy to brute force up to 3 missings words. 4 missing words can be done, but it requires a substantial financial investment to complete the search for 4 missing words in a reasonable timeframe.

More than 4 missing words is currently beyond the state of the art to solve.

Final Thoughts

In conclusion, the journey to recover a missing word from your mnemonic phrase can be daunting, yet it is not insurmountable. The importance of these phrases in the realm of cryptocurrency cannot be overstated, as they hold the key to accessing and safeguarding your digital assets.

While the process of manually recovering a missing word is complex and time-consuming, it underscores the critical need for meticulous record-keeping and the careful handling of your recovery phrases.

For those facing this challenge, professional assistance can provide a viable solution, offering expertise and resources that greatly increase the chances of successful recovery. If you would like help recovering your mnemonic sentence, please contact us.

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