BIP39 Mnemonic Generator

Generate and validate BIP39 seed phrases locally

For testing and development only. Never use a generated phrase for a real wallet holding funds, and never paste a real recovery phrase into any website.

Generate

Click Generate phrase to create a random 12-word mnemonic.

Validate a phrase

About

Generate a BIP39 mnemonic seed phrase (12, 15, 18, 21, or 24 words) using a cryptographically secure random number source, or validate an existing phrase (its checksum is checked). Entropy is shown alongside. Everything runs locally in your browser — no phrase is transmitted or stored. For testing and development only.

    Examples

    Generate a 12-word mnemonic

    Input
    word count: 12
    Output
    abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon about
Entropy (hex): 4a3b8f7d2e1c6a9b...

    A 12-word phrase encodes 128 bits of entropy plus a 4-bit checksum = 132 bits total, rendered as 12 words from the BIP39 wordlist.

    Validate a mnemonic

    Input
    phrase: abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon about
    Output
    ✓ Valid BIP39 mnemonic
Entropy: 4a3b8f7d2e1c6a9b...
Word count: 12
Checksum: correct

    The validator confirms all 12 words are in the wordlist and that the final word's checksum matches the entropy.

    About this tool

    BIP39 mnemonic seed phrases are 12-to-24-word sequences used to generate deterministic cryptographic wallet keys. They are the human-readable form of wallet backup — writing down the words on paper is the standard recovery procedure. The words come from a standardised 2048-word English list defined in BIP39, and the final word includes a checksum computed from the entropy.

    This generator produces BIP39 seed phrases using the @scure/bip39 library with a cryptographically secure random source (crypto.getRandomValues). It also validates entered mnemonics against the wordlist and checksum. The tool shows the underlying entropy in hexadecimal for transparency.

    How to use

    1. Choose a word count

      Pick 12, 15, 18, 21, or 24 words. More words mean more entropy and a longer recovery phrase.

    2. Generate

      Click Generate to produce a fresh mnemonic from a secure random source. The underlying entropy is shown as hex below the phrase.

    3. Validate or copy

      Use the Validate tab to check an existing phrase. Click Copy to save the mnemonic. ⚠ TESTING ONLY — never use generated phrases in a real wallet.

    Use cases

    Generating test mnemonic phrases

    Create deterministic wallet test fixtures with known seed phrases for integration-testing wallet software without touching real funds.

    Learning how BIP39 works

    Inspect the entropy hex alongside the mnemonic to understand the relationship between the random bits and the word representation.

    Validating recovery phrases

    Check a recovery phrase before importing it into a wallet to confirm the checksum is valid and there are no typos.

    Common mistakes

    Mistake:Using a generated phrase in a real wallet.

    Fix:Generated phrases come from a public, non-random source in some browsers. Never use this tool to create real wallets — it is for testing and education only. Use your wallet software's own secure generation.

    Mistake:Assuming any 12-word list is a valid BIP39 phrase.

    Fix:BIP39 mnemonics include a checksum in the final word. A random list of words from the wordlist will fail the checksum check. Always validate before using a phrase.

    Mistake:Storing the phrase digitally.

    Fix:Clipboard, screenshots, cloud storage and email are all vectors for theft. Paper and a hardware wallet are the only safe storage methods for real seed phrases.

    Frequently asked questions

    Related guides

    How BIP39 Seed Phrases Work (and Why You Must Never Reuse One)

    The entropy-to-words mapping, the checksum, and the security model that makes a 12-word phrase protect an entire cryptocurrency wallet.

    References & standards

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