Seed Validator
Validate a BIP-39 mnemonic the same way wallet software does before it derives keys: every word checked against the official 2048-word English wordlist (embedded in this page), lengths of 12, 15, 18, 21 or 24 words, and a SHA-256 checksum that must match the underlying entropy. Invalid words are highlighted individually.
This tool is plain client-side JavaScript — no accounts, no server calls, no telemetry, not even a web font from a CDN. To keep it forever: press Ctrl + S (Mac: Cmd + S), choose "Webpage, Complete", and open the saved file any time — with Wi-Fi off, in airplane mode, on a machine that never touches the internet.
Validate a mnemonic
Validates a BIP-39 mnemonic the same way wallet software does before it derives keys: every word must exist in the official 2048-word English wordlist (embedded in this page), the length must be 12, 15, 18, 21 or 24 words, and the final words must encode a checksum that matches SHA-256 of the underlying entropy. Invalid words are highlighted individually, so you can see exactly where a transcription went wrong.
Typing a seed phrase on any computer is a risk in itself — for real keys, prefer validating on an offline machine using the saved copy of this page, or better, let your hardware wallet do the check. English wordlist only.
How the Seed Validator works
A BIP-39 phrase is not just a list of words — it is a reversible encoding of a random number. The entropy (128 to 256 bits) is split into 11-bit groups, and each group indexes one of exactly 2048 words in the official English wordlist. The validator first walks your phrase word by word against that list; a word that is not present — a typo, a wrong language, an autocorrect casualty — is flagged individually with its position, rather than failing the whole phrase at once. That is the difference between "something is wrong" and knowing precisely which word to fix.
Once every word is known, the validator converts them back into the raw bits and separates entropy from checksum. The checksum length is always entropy length divided by 32: four bits for a 12-word phrase, eight bits for a 24-word phrase. It hashes the entropy with SHA-256 — computed locally — and compares the leading bits to the checksum bits encoded in your final word. If they disagree, the phrase is internally inconsistent: typically one word was swapped, or two were transposed, and no wallet will derive the same keys from it twice.
The 2048-word list ships inside this page, so validation works from a saved file with the network unplugged — which is exactly how you should use it for a phrase that protects real funds. What this tool deliberately does not do: tell you which wallet a phrase belongs to, recover a lost phrase, or rate how secure the original entropy was. A valid phrase is a well-formed phrase, nothing more. The deeper mechanics are explained in our BIP-39 guide.
Seed Validator — questions
Is typing my seed phrase into this page safe? +
The page makes zero network requests and validates entirely in your browser, so nothing is transmitted — but typing a seed phrase on any shared or compromised computer is a risk regardless of this page. For real keys, save the page, go offline, and validate there; or let your hardware wallet perform the check during recovery.
What does the checksum actually prove? +
It proves the phrase is internally consistent: the bits encoded in the final word(s) match SHA-256 of the entropy encoded in the rest of the phrase. A phrase that fails checksum cannot be a genuine BIP-39 phrase — usually a transcription error. A phrase that passes is well-formed, which is not the same as being yours or being secure.
Does it support other languages or Electrum seeds? +
No. This validator checks the BIP-39 official English wordlist only — the standard used by Ledger, Trezor, COLDCARD and most hardware wallets. Electrum's older seed scheme and non-English BIP-39 wordlists use different word sets and will not validate here by design.
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