Seed phrase backup

Your bitcoin is not inside your wallet. A wallet is the phone or hardware device that holds your private cryptographic keys. A private cryptographic key (often shortened to private key) is a number that proves you can spend your bitcoin. The balances themselves sit on the blockchain, Bitcoin's shared public record of balances (Where is my bitcoin, really?).

Your seed phrase is the written backup of those keys: 12 or 24 ordinary words, in order (BIP 39). BIP means Bitcoin Improvement Proposal, a numbered standard that wallets follow. If your wallet breaks, gets lost or is stolen, those words rebuild every key on a new wallet. Without them, nothing brings your bitcoin back (What is a seed phrase?).

On an exchange, a company that holds bitcoin for you until you withdraw, the company keeps the keys. Once you hold your own keys, nobody can reset a lost backup for you. There is no help desk and no password reset (Why self-custody matters). The words also work for anyone who finds them. So a good backup does two jobs: it survives, and it stays private.

1. Remember this rule: whoever holds your words can spend your bitcoin, from anywhere.
2. Find the words your wallet showed you at setup. Lost track of them? Follow Check your wallet backup before you go on.
3. Keep the backup checklist open and tick each item as you finish a lesson.

Your first copy is handwritten. Small slips cause big trouble later: a word in the wrong spot, a "v" that looks like a "u", a missing word. Every word comes from a fixed list of 2,048 words, and the first four letters of each word are enough to tell it apart from all the others (BIP 39). The last word also carries a built-in check, so a wallet warns you when the words don't fit together (BIP 39).

1. Use the card that came with your wallet, or plain paper, and a pencil or archival ink pen.
2. Write each word in order, numbered 1 to 12 or 1 to 24, in clear block capitals.
3. Copy each word from the device screen, never from memory.
4. Read the whole list back against the screen, one word at a time.
5. Confirm the words on the device when it asks. Never type them into a computer or phone to check them.
6. Write nothing else on the card: no wallet name, no PIN and no word "bitcoin".

Paper is fine for the first days. It burns, soaks through and fades, so for the long run copy your words onto stamped or engraved stainless steel. A metal copy survives fire and flood far better than paper (Seed phrase backup).

If space on the plate is tight, stamp the first four letters of each word. No two words on the list share them (BIP 39).

1. Buy a stainless steel backup kit from its maker's own store, the same rule as for your wallet. Skip any kit or service that asks you to scan, photograph or register your words.
2. Stamp or engrave every word with its number, either the whole word or its first four letters.
3. Check the metal copy word by word against the paper copy.
4. After your restore test in lesson 5 passes, destroy the paper drafts: shred them, then burn the pieces.
5. Never cut your words into halves kept in two places. Half a seed is weaker and makes recovery fragile. To remove a single point of failure, learn about multisig.

Your backup needs a home you can reach and a burglar, guest or contractor would never think to check. It also must never become a file. A photo, note or file can be copied by malware, synced to a cloud account you forgot about, or found by anyone who gets into your email.

1. Never photograph or screenshot the words.
2. Never save them in the cloud, a notes app, an email draft, a text message or a password manager.
3. Never print them, and never read them out to a voice assistant.
4. Never type them into a website, app or chat, even one that offers to "check" or "validate" your wallet.
5. Keep the metal copy somewhere private, safe from fire and water, with no label that says bitcoin.
6. A bank safe-deposit box comes with access and seizure trade-offs. Weigh them before you pick one.
7. Tell one trusted person that a backup exists and where your instructions are kept, never the words themselves (Inheritance planning).

A backup you have never tested is a guess. A test proves your words rebuild the same wallet. Do it while the wallet holds only a small amount, as in Module 12. Each wallet shows a master fingerprint, a short code that names that wallet. Anyone can see it without being able to spend, so it is safe to write down, and it tells you a restore rebuilt the right wallet.

1. Write down the master fingerprint and the first receive address your wallet shows.
2. Hardware wallet: wipe it, or use a spare device bought direct from the maker, then restore from your metal copy on the device itself.
3. Phone wallet: use the app's Verify backup step, or restore in the same official app. Never in a different app someone points you to.
4. Check that the fingerprint and first receive address match your notes.
5. If anything is different, stop. Add no more money until it matches.
6. Repeat the test once a year with the yearly recovery drill.

Some wallets let you add a passphrase, an extra password you choose, on top of your words. The same words with a different passphrase open a completely different wallet (BIP 39). A thief who finds only your words gets the wrong wallet.

The catch: nobody can reset it. Lose the passphrase and the bitcoin behind it is gone for good. If you are just learning, skip it for now and come back once your backup is tested.

1. Choose a long passphrase made of several random words, never a pet's name or a birthday.
2. Back it up separately from your seed words, in a different place.
3. Write down the passphrase wallet's master fingerprint. A matching fingerprint on restore proves you typed the passphrase correctly.
4. Test seed plus passphrase before you move real money in.
5. Curious how a passphrase changes the odds of guessing? See the seed phrase math.

Thieves rarely guess a seed. They trick people into handing it over. Real support never needs your words, and no update, refund or prize requires them (Common bitcoin scams).

1. Treat anyone who asks for your words as a thief, whoever they say they are.
2. Ignore emails, texts and pop-ups that say your wallet must be "validated", "synced" or "migrated". Check news on the maker's own site, typed by hand, and on the Security watch.
3. Never pay a "recovery service" and never give your words to a remote helper.
4. A wallet that arrives with words already printed or filled in is compromised. Stop and contact the maker through its official site.
5. Keep your holdings private. Fewer people knowing means fewer people trying.
6. Want a printable list for family? Use the scam protection kit.

Firmware is the software inside your hardware wallet. Your words are only as strong as the randomness that made them. In 2026 Coinkite disclosed that an integration error caused some COLDCARD firmware to create seeds with far less randomness than intended (Coinkite advisory). Attackers recreated affected seeds on their own computers. Galaxy Research's August 25, 2026 tally put confirmed losses at about 1,789 BTC from 8,865 addresses (Cointelegraph).

Updating the firmware did not change seeds that already existed. Affected owners had to create a new seed on fixed firmware and move their bitcoin to it (COLDCARD migration guide).

1. Update firmware before you create a seed, not after.
2. Add your own randomness, such as dice rolls, if your wallet supports it.
3. Keep a private note of which wallet and firmware version created each seed, and the date.
4. When an advisory names your wallet, check on the Security watch whether it affects the seed itself or only the device.