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BIP39 mnemonic generator

Generate a valid BIP39 recovery phrase, or verify one you already have — entirely offline.

Phrase to verify (optional)
Output
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BIP39 mnemonic generator
A BIP39 mnemonic is the 12-to-24-word recovery phrase behind almost every modern cryptocurrency wallet — Bitcoin, Ethereum and most hardware wallets all derive their keys from one. This tool generates a fresh, cryptographically random phrase with a valid checksum, or checks a phrase you already have without ever sending it anywhere.
Choose how many words you need — 12, 15, 18, 21 or 24, corresponding to 128 through 256 bits of entropy — and which of the five supported wordlists to draw from: English, Czech, French, Spanish or Italian. The separator between words, word numbering and wordlist indices are optional formatting toggles, and you can reveal the underlying entropy as hexadecimal if you need it for another tool.
Paste an existing phrase into the second field to verify it instead of generating a new one. The check names exactly what went wrong: an unrecognized word (a typo, or the wrong wordlist language selected), an unsupported word count, or a checksum mismatch — which usually means a word is out of order or was swapped for a similar one. A phrase can look plausible, every word spelled correctly, and still fail: BIP39 encodes an error-detecting checksum into the last word or two, and this tool checks it exactly the way a wallet would.
Every calculation — the random entropy, the SHA-256 checksum — runs locally in your browser through the Web Crypto API. Nothing is ever transmitted, logged or stored, and this tool never derives or displays a wallet address or private key from your phrase; it only generates and validates the words. Copy the result, download it as a .txt file, or send it straight to another tool's input.
FAQ
What word counts does BIP39 support, and what do they mean?
BIP39 phrases come in five lengths: 12, 15, 18, 21 or 24 words, encoding 128, 160, 192, 224 or 256 bits of random entropy respectively. More words means more entropy and a slightly stronger phrase, but any of the five lengths is considered secure when the words are genuinely random.
Does this tool show me a wallet address or private key?
No. It only generates and validates the mnemonic phrase itself. It never derives a seed, private key or address from it, so it can't tell you whether a phrase actually controls any funds — for that you need your wallet software.
What does an 'unknown word' error mean when I verify a phrase?
One of the words you entered isn't in the selected wordlist. Check the spelling first, and if the phrase was generated in a different language, switch the wordlist language option to match it.
Why does a phrase fail with a checksum error even though every word looks right?
The last word (or the tail bits of it) encodes a checksum over the rest of the phrase. If two words are swapped, one is replaced by another valid word, or the phrase is incomplete, every individual word can still be valid while the checksum no longer matches.
Is my phrase or entropy uploaded anywhere?
No. Generation and verification run entirely in your browser using the Web Crypto API — nothing is sent to a server, logged or stored. Treat any recovery phrase as sensitive regardless: write it down on paper rather than saving it in a text file or screenshot.