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BIP-39 Mnemonic Generator

Generate a fresh seed phrase — 12 to 24 words, drawn from your browser's secure randomness, entirely offline.

A seed phrase is a real, usable secret the moment it's generated.

Anyone who sees these words controls every account they derive — forever, not just until you close this tab. Write it down offline before using it for anything; don’t rely on a screenshot, a note app, or your clipboard history.

What a seed phrase actually is

A BIP-39 mnemonic encodes a block of random entropy (128-256 bits, depending on word count) as a sequence of words from a fixed 2048-word list, plus a built-in checksum. That entropy is the actual secret — the words are just a human-friendly, error-checked way to write it down. From that one secret, a wallet deterministically derives every account and address it will ever show you.

When you’d generate one outside a wallet app

Mostly for development — spinning up test/burner wallets for a script, seeding a local test environment, or generating throwaway accounts for a testnet. For anything meant to hold real value, generating the phrase inside your actual wallet software (ideally a hardware wallet) keeps the raw entropy from ever touching a general-purpose browser tab in the first place.

How this tool works

Generation uses @scure/bip39 (via viem) drawing from the Web Crypto API’s CSPRNG. Nothing is sent to a server, logged, or stored — the phrase exists only in this tab’s memory until you reload or navigate away.

Frequently asked questions

Yes — generation goes through @scure/bip39 (a widely-used, audited implementation), which draws from the Web Crypto API's CSPRNG (crypto.getRandomValues), the same source browsers use for TLS and other security-critical randomness. It's not Math.random() or anything homegrown.

Word count reflects the underlying entropy: 12 words = 128 bits, 24 words = 256 bits. 128 bits is already computationally infeasible to brute-force and is what most wallets default to; 24 words adds margin some people prefer for long-term cold storage. Both are secure in practice.

Write it down on paper (or stamp it in metal) immediately, store it somewhere offline and physically secure, and only then import it into actual wallet software if you intend to use it. Never store it as a screenshot, a note-app entry, or a message to yourself.

No — this only generates new, random phrases. It has no way to look up or recover a phrase you've lost; nobody does, which is the entire point of a seed phrase being the sole backup for its accounts.

No. Generation and display happen entirely in your browser's memory — nothing is sent over the network, logged, or persisted. Reloading the page clears it completely.

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