BIP39 Mnemonic Generator

Draw fresh entropy from your browser’s cryptographic random generator and turn it into a BIP39 mnemonic. Pick 12, 15, 18, 21 or 24 words, see the hex entropy behind it, and copy the phrase. It runs entirely on this page.

This BIP39 mnemonic generator builds a seed phrase the same way a wallet does: it pulls random bytes from the Web Crypto generator, appends a SHA-256 checksum, and maps each 11-bit chunk to a word from the official 2048-word BIP39 list. Choose how many words you want and you get a valid crypto mnemonic plus the raw entropy in hex, so you can check the math yourself. Nothing is uploaded — the seed phrase generator works offline once the page has loaded. The wordlist and checksum are the real spec, so a phrase made here validates in any BIP39-compatible tool.

Entropy is drawn from your browser’s cryptographic random generator and never leaves this page. Treat any phrase you plan to use as a real secret — generate it offline and never paste an existing wallet’s seed words here.
    Strength
    128-bit entropy · 12 words · 4-bit checksum
    Entropy (hex)
    —

    How it works

    1. 1

      Choose a word count

      Pick 12 through 24 words. More words means more entropy — 12 words is 128-bit, 24 words is 256-bit.

    2. 2

      Generate a phrase

      Press New phrase to draw fresh random bytes. Each press gives a different mnemonic with its own checksum.

    3. 3

      Copy or download

      Copy the space-separated bip39 words, or save them to a text file. The hex entropy is shown alongside so you can verify it.

    Instant & 100% private — nothing is uploaded

    Everything runs locally in your browser. Your code, text and files are processed on your own device and are never sent to a server — so there are no upload waits, no size limits from us, and nothing is ever stored or logged.

    Frequently asked questions

    Is the randomness safe to use?
    The entropy comes from crypto.getRandomValues, the browser’s cryptographic random source, not Math.random. That said, generating a real wallet seed on an online device is risky — use this to learn or to test, and generate anything you’ll actually fund on an offline machine.
    How many words should I pick?
    Twelve words (128-bit) is standard and plenty for most wallets. Twenty-four words (256-bit) adds headroom and is common on hardware wallets. Fifteen, eighteen and twenty-one sit in between.
    What is the checksum for?
    The last few bits of a BIP39 mnemonic are a SHA-256 checksum of the entropy. It lets a wallet catch a mistyped word. This tool computes that checksum with crypto.subtle, so every phrase it prints is valid.
    Does the phrase leave my browser?
    No. Generation, the checksum and the wordlist lookup all happen locally in JavaScript. There is no network request and no logging.
    Can I recover a wallet from a phrase made here?
    A phrase from this crypto mnemonic tool is a standard BIP39 phrase, so any BIP39 wallet can import it. But treat it as a live secret the moment you do — anyone with the words controls the funds.

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