Free practice tool
BIP39 practice studio
The trainer for wallet people. Practice the write-down-and-restore ritual with 12- or 24-word phrases built from the real BIP39 wordlist. Their checksum is broken on purpose, so they fail the BIP39 check and must never be used to secure funds. The broken checksum is also the lesson: the last word of a real phrase was never yours to choose.
Fake phrases only, checksum broken on purpose. Generated in your browser, never sent, never stored.
1 · Meet your practice phrase
Words from the real BIP39 list, so the ritual feels real. But the closing word is chosen to fail the checksum, so the phrase guards nothing and never will.
Peeking is allowed in practice. The real ritual shouldn’t need it. That’s what the read-back step is for.
Write it down properly (yes, actually)
- Pen and paper. Not a screenshot, not a photo, not a notes app.
- Copy the numbers too: “7. ribbon” beats a bare word when your hands are shaking.
- Print letters, and slow down on lookalikes. The drill below will show you why.
- Read it back word by word against the screen before you call it done.
There is deliberately no copy button here. The practice is the pen.
Why the last word isn’t arbitrary
2 · The restore drill
Rebuild the phrase from your paper, in order, by tapping words in the bank below. Some bank words are lookalike traps one pen-stroke away from the right word. That is the same trap bad handwriting sets on a real restore.
There is nothing to type anywhere on this page. You can only tap words this page generated. That is what makes entering a real phrase impossible here, not merely discouraged.
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Word bank: your words, in the wrong order, plus impostors
Restored perfectly, trap words dodged. That’s the entire skill, and now you’ve done it once before it mattered.
3 · Do or don’t?
Seven quick calls, answered for a REAL phrase. The practice one already broke half these rules by existing on a screen.
Take a photo of the phrase “just as backup”
A photo puts the phrase in your camera roll, and from there into cloud sync, backups, and every app with photo access. It’s the single most common way seeds leak.
Keep it in a synced notes app until the metal plate arrives
“Temporary” readable text in the cloud is still readable text in the cloud. Whoever gets into the account, by phishing, SIM swap or breach, gets the wallet, this week.
Type it into a website that offers to “validate” your backup
A site asking for a real phrase is a scam by definition, this one included, if it ever asked. Your wallet can verify the checksum offline. No website is ever part of that.
Stamp it into metal and store it where you’d keep a passport
Offline, fireproof, in a place you already treat as valuable. That’s the model. Metal can’t be phished and doesn’t dissolve in a burst pipe.
Read it out to “wallet support” who contacted you about suspicious activity
Nobody legitimate asks for it. Not support, not an exchange, not a hardware-wallet maker. Whoever asks for the words IS the attack, and they always bring urgency.
Do a read-back check right after writing it down
Thirty seconds comparing paper to screen catches the swapped word and the lookalike letter that would otherwise surface years later, at the worst possible moment.
Practice the whole ritual once with a fake phrase
You’re doing it now. The first restore of your life shouldn’t also be the one that matters. A practice phrase with a broken checksum is the only safe phrase to rehearse with.
That’s the drill. The reflexes you want: paper, numbers, read-back, lookalike-paranoia, and instant suspicion of anyone who asks for the words.
How this works (and why it’s safe)
Practice phrases are drawn in your browser with crypto.getRandomValues from the BIP39 English wordlist served from this site (2,048 words, byte-identical to the canonical list; see its provenance note). For each phrase the page computes, with WebCrypto SHA-256, which closing words would make the checksum valid: 128 of 2,048 for 12 words, 8 for 24. It then picks the last word from outside that set, so every phrase fails the checksum. One honest caveat: turning a phrase into a seed does not depend on that check, and the BIP39 spec only requires software to warn on a bad checksum. A permissive wallet could still derive a seed from one of these. That is why the rule here is firmer than “no wallet will take it”: a checksum-failing phrase must never be used to secure funds. The drill has no text input. It only compares taps against the phrase it generated seconds earlier, so a real phrase cannot enter this page even on purpose. Nothing is sent, nothing is stored, and reloading forgets the phrase forever.
Rehearse here. Keep the real one in a vault.
The working copy of a real phrase belongs where nothing readable ever leaves the device. Sealby encrypts it on your iPhone with keys in the Secure Enclave. No account to phish, deniable if it matters.
iPhone & iPad · iOS 17+ · Free