BIP39 Mnemonic Generator
Token GenerationProcessed locally in your browser using the Web Crypto API. Nothing is sent to any server.
How It Works
This tool generates BIP39 mnemonic phrases using cryptographically secure randomness
from crypto.getRandomValues(). Each phrase includes a SHA-256 checksum that can detect
typos and errors. The tool also validates existing mnemonic phrases against the BIP39 standard.
Algorithm Details
- Wordlist: BIP39 English (2048 words)
- Entropy:
crypto.getRandomValues()— hardware-level CSPRNG - Checksum: SHA-256 of entropy, first
entropy_bits / 32bits - Word encoding: Each word represents 11 bits (
log2(2048) = 11) - Supported lengths: 12 (128-bit), 15 (160-bit), 18 (192-bit), 21 (224-bit), 24 (256-bit)
- Implementation: Pure TypeScript + Web Crypto API — no external libraries
How BIP39 Works
- Generate random entropy (128–256 bits)
- Compute SHA-256 hash of the entropy
- Append the first
entropy_bits / 32bits of the hash as a checksum - Split the combined entropy+checksum into 11-bit groups
- Map each 11-bit value to a word from the 2048-word BIP39 wordlist
Common Use Cases
- Understanding BIP39 mnemonic generation for educational purposes
- Validating mnemonic phrases for correctness
- Learning about deterministic key derivation
- Testing BIP39 implementations
Frequently Asked Questions
What is BIP39?
BIP39 is a standard for generating deterministic mnemonic phrases — human-readable sequences of words that can be used to derive cryptographic keys. It uses a 2048-word English wordlist and includes a checksum to detect errors.
How does the checksum work?
The checksum is derived from a SHA-256 hash of the random entropy. For a 12-word mnemonic, 4 checksum bits are appended, creating 132 bits total split into 12 groups of 11 bits. The checksum ensures that a single typo can be detected.
Is this safe for generating real wallet mnemonics?
This tool uses cryptographically secure randomness and runs entirely in your browser — no data is transmitted. However, for maximum security with real assets, consider using dedicated hardware wallets or offline tools.
Privacy Note
This tool runs entirely in your browser. Your input is never uploaded, stored, or sent to any server.
Disclaimer: This tool is provided for educational and informational purposes only. The results do not constitute professional security advice. Use at your own discretion.