BIP39 Verifier
Advanced security analysis for your mnemonic phrases.
About the BIP39 Mnemonic Verifier
The BIP39 Mnemonic Verifier is a lightweight, privacy-first web utility created to give users immediate confidence when working with recovery phrases. It performs one core task with absolute clarity: it checks whether every word in a 12-word or 24-word phrase belongs to the official English BIP39 wordlist of 2048 words. Nothing more, nothing less.
Unlike full wallet recovery tools that derive seeds, validate checksums, and generate addresses, this verifier deliberately stops at wordlist membership. That narrow focus makes it exceptionally fast, transparent, and trustworthy for the most common real-world need — confirming that a copied or handwritten phrase does not contain typos, wrong words, or non-BIP39 vocabulary before any further steps are taken.
Every operation happens exclusively in your browser. The 2048-word list is embedded as a static JavaScript array. When you paste a phrase and click Analyze All, the input is cleaned (whitespace trimmed, lowercased), split into words, counted, and compared against that fixed list using simple array lookups. If the count is wrong or any word is missing from the official list, you receive an immediate, clear error message highlighting the problem words. If everything matches, a green confirmation appears — all within milliseconds and without a single network request.
Advanced tabs provide optional deeper insight for educational or debugging purposes. You can add a passphrase to see how it affects seed derivation, view the extracted entropy in hex, observe the master private key and chain code, and inspect child keys for six common derivation paths (Bitcoin Legacy, Native SegWit, Nested SegWit, Ethereum, Binance Chain, Cosmos). These values are computed locally using Web Crypto APIs and never leave your device.
The security strength tab lets you simulate partial knowledge attacks by adjusting the “Known Words” slider, recalculating remaining entropy and brute-force time estimates in real time. Again — all calculations are performed client-side.
Why this matters: Most mnemonic mistakes happen at the word level — typos, autocorrect errors, memory slips, or corrupted copies. Catching these early saves time and reduces risk. By limiting scope to wordlist validation in the primary flow, the tool eliminates almost every privacy concern. There is no server communication, no persistent storage, no tracking, no analytics, and no third-party scripts. The entire application is static, hosted on platforms such as GitHub Pages, and can even function offline after the first load.
This verifier is not a replacement for full wallet recovery software that performs checksum validation, entropy checks, and address derivation. It is a fast, zero-risk first filter — a sanity check you can run on any device, in any environment, with complete confidence that your phrase remains under your sole control.
Use it as the first step in any mnemonic verification workflow. If it passes, proceed to more comprehensive tools when you are ready to act on the phrase.
How to Use the BIP39 Mnemonic Verifier
Paste Your Mnemonic Phrase
Click into the large textarea at the top of the page. Paste your 12-word or 24-word BIP39 recovery phrase directly from your wallet software, secure note, or paper backup. Avoid typing manually whenever possible — copy-paste reduces transcription errors. The tool automatically trims leading/trailing whitespace and collapses multiple spaces, so messy formatting from emails or screenshots is handled gracefully.
Add Passphrase (Optional)
If your wallet used an additional passphrase (sometimes called the “25th word”), enter it in the field below the textarea. Leave this blank if no passphrase was set. Changing or removing the passphrase will produce completely different seed and key values — this is expected BIP39 behavior and lets you verify how sensitive your seed is to this extra secret.
Click Analyze All
Press the large blue Analyze All button. Within a second or two the tool finishes processing. Switch between the three tabs to see results:
- Basic Validation — green success if all words are valid BIP39 entries and count is correct; red alert with listed invalid words or wrong-count message otherwise
- Entropy & Keys — only appears if basic validation passes; shows entropy hex, seed, master private key, chain code, and child keys for six common paths
- Security Strength — displays entropy bits, theoretical attack surface, and brute-force time estimates; adjust “Known Words” to simulate partial knowledge
Tips for best results: Always paste from a trusted source. Use the Clear button between tests to reset everything. For maximum privacy, run the tool offline after the first load or on an air-gapped device when checking real phrases. Remember this is a wordlist sanity checker — if you need full checksum and derivation validation, use a complete wallet recovery tool after the basic check passes.
Frequently Asked Questions
Is it safe to paste my real mnemonic phrase here?
The tool runs 100% in your browser — no data is sent anywhere, no storage is used, and nothing is logged. However, we strongly recommend using it only for test phrases or on an air-gapped machine when dealing with real funds of significant value. Even though the code is open and auditable, human habits (clipboard leaks, screen recording, shared devices) introduce risk outside our control. Treat this as a quick wordlist sanity check, not a production wallet recovery step.
Does it validate the checksum or entropy?
No — the core validation checks only wordlist membership and correct word count (12 or 24 words). It intentionally does not verify checksum bits or entropy validity. This keeps the tool fast, simple, and maximally private. If you need full BIP39 compliance (checksum + derivation), use a dedicated wallet recovery application after confirming wordlist validity here.
What wordlist does it use?
The official English BIP39 wordlist of exactly 2048 unique words, as defined in the Bitcoin Improvement Proposal 39. No other languages are supported at this time.
Why does it say “invalid word” when I think the word is correct?
Most often this is a typo, autocorrect change, or case issue (although case is normalized). Double-check your source. Some wallets display shortened or alternative word forms — the tool only accepts the exact 2048 official words. If the word is genuinely missing from the list, it is not BIP39-compliant.
Can I use it offline?
Yes — after the first load, the entire application (including the wordlist) is cached by your browser. You can disconnect from the internet and continue using it. This makes it suitable for air-gapped environments.
Does it store my phrase or passphrase?
No. The tool uses no cookies, localStorage, sessionStorage, or any persistent mechanism. Everything is discarded when you refresh or close the page. The Clear button resets the form instantly.
Is this a replacement for my wallet software?
No — it is a quick wordlist sanity checker only. It does not recover wallets, generate addresses, sweep funds, or perform full BIP39 validation. Always use official wallet software for final recovery and key management.