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BIP39 Mnemonic Generator — Offline, Client-Side, Never Transmitted

Generate a BIP39 mnemonic seed phrase — the standard 12 or 24-word recovery phrase used by Bitcoin and most crypto wallets — using cryptographically secure randomness computed entirely in your browser. A seed phrase controls real funds, so this never sends it anywhere: not to a server, not in analytics, not in a network request of any kind.

How to use BIP39 Mnemonic

  1. Choose 12, 15, 18, 21 or 24 words.
  2. Generate using cryptographically secure randomness.
  3. Write the phrase down offline — never store it digitally.
  4. Verify the checksum word is valid before relying on it.

Frequently asked questions

Is it actually safe to generate a seed phrase in a browser?
The generation uses the Web Crypto API's cryptographically secure random number generator entirely client-side, and nothing is transmitted over the network — but for real funds, many security-conscious users still prefer generating on an air-gapped device or hardware wallet specifically to eliminate any possibility of a compromised browser or extension. Understand that trade-off before using any browser-based generator for a wallet holding real value.
Why does the phrase include a checksum word?
The final word of a BIP39 phrase is a checksum encoding a hash of the preceding words, catching a mistyped or misremembered word rather than letting a wallet silently derive the wrong keys.
Should I ever type a seed phrase into a website?
No — never enter an existing seed phrase into any website, including this one. A legitimate wallet only asks for your seed phrase inside its own dedicated recovery flow, offline or in the wallet software itself.
Where should I store a generated seed phrase?
Written on paper or metal, offline, never as a photo, text file, or password manager entry connected to the internet — a digital copy of a seed phrase is a direct target for malware.

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