Metal backup

A metal backup stores your seed phraseGlossarySeed phrase (recovery phrase)A sequence of usually 12 or 24 words from which your wallet derives all its private keys. Anyone who knows the words has full access to your bitcoin – so they belong in an offline backup and never in anyone else’s hands.On the learning path: Stage 5 · Step 3 – Backing up your seed phrase →In the glossary →× on steel or titanium. Unlike paper, it stays readable after a fire or a flood.

Common designs are plates with a grid into which you punch dots with a hammer and centre punch, stamped or engraved plates, and capsules with individual letter tiles. The first four letters of each word are enough, because in the BIP 39GlossaryBIP 39 (standard for seed words)The widely used standard that turns random data into 12 to 24 words from a fixed list of 2,048 words. Your wallet calculates all its keys from these words – BIP 39 is behind most seed phrases.On the learning path: Stage 5 · Step 3 – Backing up your seed phrase →In the glossary →× word list they identify every word uniquely.^[1]

What independent tests show

Jameson Lopp has tested 75 metal backups against heat, corrosion and pressure. His conclusion: the fewer parts, the fewer things can go wrong. Single plates with a punching grid offer the best value for money. At around 1,100 °C (2,000 °F), devices with aluminium housings melted; in two stainless steel devices with rails, letter tiles shifted or fell out. Avoid products where the manufacturer could know your keys.^[2],[3]

What to watch out for

• Metal protects against fire and water, not against thieves: whoever finds the plate has access to your bitcoin. Keep it as you would cash, without a ‘Bitcoin’ label.
• After transferring the words, check every word and the order – ideally with a test recovery.
• A passphraseGlossaryPassphrase (the ‘25th word’)An extra word of your choice added to your seed phrase. The same words then produce a completely different wallet. This protects you if someone finds your words – but if you forget the passphrase, access is lost for good.On the learning path: Stage 5 · Step 3 – Backing up your seed phrase →In the glossary →× doesn’t belong on the same plate.

Where to keep the plate and whether a second copy makes sense is explained in Backing up your seed phrase.