Generate BIP39 seed phrases (12/15/18/21/24 words) offline in your browser. Useful for cryptocurrency wallets.
Generate cryptographically secure BIP39 mnemonic seed phrases in 12, 15, 18, 21, or 24 words — entirely in your browser. BIP39 (Bitcoin Improvement Proposal 39) is the standard used by most cryptocurrency wallets (Bitcoin, Ethereum, Solana, and countless others) to turn high-entropy random numbers into a human-readable set of words that can be written down and restored. Everything runs locally using your browser's secure random source; nothing is sent over the network.
Pick the word count
12 words (128 bits of entropy) is the common default; 24 words (256 bits) is the highest strength. 15, 18, and 21 are the intermediate sizes.
Click Generate
A fresh mnemonic is produced from your browser's cryptographic random source and displayed as a numbered grid you can read or write down.
Optional: inspect the derived seed
Expand the Show derived seed panel to see the 64-byte BIP39 seed (hex) that a wallet would derive from the mnemonic using PBKDF2.
Copy and store safely
Copy the mnemonic to your clipboard or write it down. Store it offline — paper, metal backup, or a hardware wallet — never in plaintext on the cloud.
BIP39 is a standard for representing a random cryptographic seed as a sequence of 12–24 English words drawn from a fixed 2048-word list. Most cryptocurrency wallets use BIP39 so that a human-readable backup phrase can be written down and later restored into any compatible wallet.
12 words (128 bits of entropy) is plenty for practical security and matches what most wallets default to. 24 words (256 bits) offers a wider security margin. 15/18/21 exist for completeness and are rare in practice.
The entropy is sourced from WebCrypto — the same primitive wallets use in-browser — and runs entirely client-side. Even so, for large balances, prefer a hardware wallet and an air-gapped environment. Never paste the phrase into a website, cloud note, or chat.
A wallet turns the mnemonic into a 64-byte binary seed using PBKDF2 with 2048 iterations and an optional passphrase. That seed is the actual input to HD-key derivation (BIP32). This tool shows the no-passphrase seed for inspection only — you don't need to copy it to back up your wallet; the mnemonic is enough.
Yes. The mnemonic fully controls every wallet and account derived from it. Treat it like a master key: keep it offline, never share it, and beware of anyone asking for it under any pretext.