How to use the generator
- Choose a word count. The boxes show how many bits of entropy and checksum that length uses.
- Press Generate for fresh random entropy, or Load test vector for an official, reproducible example.
- Read the mnemonic and its entropy. The last bits of the final word are the checksum.
- Copy it into your test project, or press Clear. It is erased when you leave the page.
What is a BIP39 generator?
A BIP39 generator turns random data (entropy) into a list of words from the standard 2048-word list. The words are a human-friendly way to write down that random number. Wallets then turn the words into a 512-bit seed from which keys are derived.
Generating a mnemonic is just encoding randomness: the quality of the result depends entirely on the quality of the random source and on who could see it.
12 vs 24 words
Every length is a different amount of entropy plus a checksum of one bit per 32 bits of entropy.
| Words | Entropy (ENT) | Checksum (CS) | Total bits |
|---|---|---|---|
| 12 | 128 | 4 | 132 |
| 15 | 160 | 5 | 165 |
| 18 | 192 | 6 | 198 |
| 21 | 224 | 7 | 231 |
| 24 | 256 | 8 | 264 |
12 and 24 words are by far the most common. 15, 18 and 21 are valid BIP39 but supported by fewer wallets.
Entropy and the checksum
The generator takes the SHA-256 hash of the entropy, appends its first ENT/32 bits, and splits the result into 11-bit numbers. Each number selects a word. Because the final word carries the checksum, a typo in any word is usually detected. The checksum page shows every step with real test vectors.
Where the randomness comes from
This page uses crypto.getRandomValues, which asks the operating system’s cryptographically secure random number generator. It does not use Math.random, mouse movement, or text you type. If secure randomness is unavailable, the Generate button is disabled.
Online vs offline generation
Running in the browser means the words are never sent to a server — but it does not make a website trustworthy. The code you receive could be changed, and extensions or malware on your device could read the page. That is why this generator is labelled for testing and learning.
For a real wallet, prefer a hardware wallet, or download the standalone offline file, check its SHA-256, and run it on a device with networking turned off.