Runs in your browser only

BIP39 Mnemonic Validator

Sanity-check a BIP39 seed phrase locally. Word count and wordlist membership are validated in your browser. Nothing is uploaded, stored, or transmitted to any server.

Security note: never paste your real seed phrase into a website you don't fully trust. This tool runs entirely client-side (you can verify in DevTools → Network), but as a habit, use offline validators (ian-coleman/bip39 saved to disk, hardware wallet dry-runs) for production wallet seeds. Use this tool for educational sanity-checking, not for validating live wallet seeds.

Mnemonic words (space-separated)

How BIP39 mnemonic checking works

BIP39 mnemonics encode a seed plus a checksum. The checksum is the first N/32 bits of SHA-256 of the entropy, where N is the entropy size (128, 160, 192, 224, or 256 bits — corresponding to 12, 15, 18, 21, or 24 words). A valid mnemonic must (a) have a valid word count, (b) all words drawn from the BIP39 wordlist, (c) the encoded checksum matches.

This tool checks (a) and partially (b) — using a sample of the BIP39 wordlist. Full validation including the checksum requires the complete wordlist and SHA-256 — best done with offline tools that you've verified yourself.

Recommended offline validators

ian-coleman/bip39: open-source HTML/JS tool. Save the page to disk, disconnect from internet, validate locally.
Trezor Suite / Ledger Live: dry-run import shows whether your mnemonic produces expected addresses without committing.
btcrecover: command-line tool with full BIP39 validation and partial-word recovery.

Forgot the password / passphrase?

If you have the seed but forgot the BIP39 passphrase (25th word) or wallet password — that's recoverable for typical cases. Run a free analysis.

Run Free Analysis