The BIP39 word list is a standardized set of 2048 English words that forms the foundation for your crypto wallet’s seed phrase (also known as a recovery phrase).
The list is the key to modern wallet security, and it allows you to restore your assets on a new device if your original is lost or broken. The standard ensures that a phrase generated in one wallet can be used in another wallet — essentially, the seed phrase is the master key to your cryptocurrency.
This article explains the technical standard behind your seed phrase. We will cover how a random number is converted into a memorable phrase, why these specific 2048 words were chosen, and how this powerful standard enables interoperability between different wallet software.
If you have a partial or incorrect seed phrase and need assistance, we’re here to help. Datarecovery.com provides free evaluations, and all crypto recovery services are supported with a comprehensive no data, no charge guarantee. Call us at 1-800-237-4200 or submit a case online to get started.
What is BIP39? The Universal Standard for Wallet Recovery
BIP39, which stands for Bitcoin Improvement Proposal 39, is a technical design document that has become the industry standard for creating and managing wallet backups.
Introduced in 2013, it solved a major problem in the early days of crypto: wallet incompatibility. Before BIP39, many wallets used their own proprietary backup methods, meaning a backup from one wallet could not be used on another. That locked investors into a single software provider — which didn’t vibe well with the “uncentralized” appeal of Bitcoin, Ether, and other popular cryptocurrencies.
BIP39 changed this by creating a universal language that almost all modern non-custodial wallets now use. If you’ve got a crypto wallet, you’ve probably written down a BIP39 seed phrase at some point (or at least, we hope you took that step).
Here’s an example of a BIP39 keyphrase (to our knowledge, this seed phrase isn’t associated with any wallet — we used an online generator to create it for educational purposes):
arrow foam seed monster girl sugar office parade then canoe melt say
That reads like nonsense, but it’s literally the only thing you’d need to access an associated wallet.
How a Seed Phrase Is Created: From Random Numbers to Words
A seed phrase is the human-readable representation of a very large, random number that secures your entire wallet. The BIP39 standard outlines a precise, three-step process to convert this number into your phrase:
1. Generating Randomness (Entropy)
The process begins by generating a long string of random 1s and 0s, known as entropy. This is the cryptographic heart of your wallet’s security. For a 12-word phrase, 128 bits of entropy are generated; for a 24-word phrase, 256 bits are used. The randomness of this initial number is critical, as it ensures your wallet is unique and practically impossible to guess.
If you’ve taken advanced computer classes, you might note that true randomness is incredibly difficult to program. Software-based wallets typically use a special type of algorithm called a Cryptographically Secure Pseudorandom Number Generator (CSPRNG) to produce a sequence of numbers that is statistically random (though not perfectly random, it’s still thought to be uncrackable).
Hardware wallets may use a True Random Number Generator (TRNG) chip, which gets closer to a philosophical idea of “randomness” by measuring things like variations in voltage and temperature to create entropy.
2. Adding a Checksum for Error-Checking
To prevent errors from a simple typo when you write down or enter your phrase, the BIP39 process includes a built-in integrity check. A small piece of data called a checksum is created by hashing the initial entropy with a cryptographic algorithm (SHA256).
The first few bits of this hash are then appended to the end of the entropy string. When you later import your phrase into a wallet, the software performs the same calculation. If the checksum doesn’t match, the wallet will alert you that the phrase is invalid, saving you from restoring an incorrect (and empty) wallet.
3. Mapping Binary to the BIP39 Word List
The combined string of entropy and checksum bits is then divided into groups of 11 bits. Each 11-bit group represents a number between 0 and 2047. This number is used as an index to look up a word from the official, alphabetically sorted BIP39 word list.
For a 12-word phrase, the 132 bits (128 of entropy + 4 of checksum) are split into twelve 11-bit sections, each corresponding to one word in your final phrase.
The 2048 Words: Why This Specific List?
So, why use words like arrow, seed, and monster?
The BIP39 word list was engineered to be as user-friendly and error-proof as possible. The words were chosen based on the following criteria:
- Mathematically Precise: The list contains exactly 2048 words because 2^11 equals 2048. This means that an 11-bit string of binary can represent precisely 2048 different combinations, making the mapping from the binary data to the word list perfect.
- Unambiguous: The first four letters of every word on the list are unique. That allows wallet software to identify the word unambiguously after just four characters are entered.
- Simple and Distinct: The list avoids words that sound similar or are easily confused, such as “woman” and “women” or “build” and “built”.
While the English list is the most common, the BIP39 standard also supports lists in other languages, including Spanish, French, Italian, Japanese, and Chinese. However, we recommend using the English list, as it has the most universal support across all wallets.
How BIP39 Enables Wallet Interoperability
The greatest strength of the BIP39 standard is that it decouples your assets from any single wallet provider. Because major hardware wallets like Ledger and Trezor and software wallets like MetaMask all adhere to the BIP39 standard, they can all interpret the same seed phrases.
In other words: If you generate a seed phrase with one wallet and that device is lost or the company goes out of business, you can simply download a different compatible wallet, select the “restore” option, and enter your original phrase. The new wallet will use the BIP39 standard to regenerate the same master key and provide access to your funds on the blockchain.
Note: While the seed phrase is universal, wallets sometimes use different derivation paths (standards like BIP44, BIP49, and BIP84) to generate specific addresses from the master key. If you restore a wallet and it appears empty, you may need to select a different derivation path in the wallet’s settings to find your funds.
The Security of the BIP39 Standard
A common concern is whether an attacker could simply guess a seed phrase. Fortunately, this isn’t really possible:
- A 12-word phrase has 2048^12 possible combinations, which is approximately 5.4 x 10^39. That’s a 5 followed by 39 zeroes.
- A 24-word phrase has 2048^24 possible combinations, or roughly 3 x 10^79.
These numbers are astronomically large — and we’re using the term “astronomical” literally, in this case. For perspective, the number of atoms in the known universe are estimated at around 10^78.
Even the world’s most powerful supercomputers could not guess a specific phrase in a human lifetime (though quantum computers may be able to crack all cryptography at some point in the future).
The bottom line: The security of the BIP39 standard is immense. The primary threat to your assets is not a brute-force attack but the physical or digital theft of your seed phrase.
Seed Phrase Recovery from Datarecovery.com
The BIP39 word list is the core component of a standard that makes cryptocurrency self-custody both secure and accessible. Of course, it’s not a perfect solution to the inherent problems of crypto — humans have trouble with keeping traditional passphrases secure. People frequently lose parts of their seed phrases, or worse, they store them in a way that makes them susceptible to crypto scams.
If you have lost access to a wallet but have a partial or mistyped seed phrase, Datarecovery.com can help. The deterministic nature of the BIP39 standard means recovery may still be possible, and we specialize in advanced techniques to reconstruct seed phrases and restore access to your digital assets.
Contact our experts at 1-800-237-4200 or submit a case online for a free, confidential evaluation.
