What is a Seed Phrase?

A seed phrase (recovery phrase, mnemonic) is a 12-, 18-, 24-, or 25-word sequence per BIP-39 that derives all of a wallet's private keys. It is shown once during initial wallet setup and must be written down and stored securely; anyone with the seed can recover the wallet and move the funds. Rules: (1) never upload it to cloud services (iCloud, Google Drive, email); (2) never photograph it digitally; (3) no support agent will ever ask for it — fake 'Ledger support' is among the most common phishing vectors; (4) prefer metal backup plates (Cryptosteel, Billfodl) for protection against fire, flood, and earthquake; (5) keep at least two redundant copies in geographically separate locations. For higher-value setups, an optional 25th-word passphrase adds a voluntary layer on top of BIP-39 — strong protection, but if forgotten the funds are unrecoverable. Multisig configurations (Casa, Unchained Capital) eliminate single-seed risk by requiring m-of-n approvals.