A 12 or 24-word backup phrase that generates your private keys — the master recovery key for your crypto wallet.
A seed phrase (also called recovery phrase or mnemonic phrase) is a sequence of 12 or 24 randomly generated words that serves as the master backup for a cryptocurrency wallet. The seed phrase mathematically generates all private keys and addresses associated with the wallet, meaning anyone who has your seed phrase has full access to all your crypto. This is the most critical piece of information in crypto self-custody — it should be written on physical material (not stored digitally), kept in a secure location (ideally multiple copies in different locations), and never shared with anyone. There is no 'forgot my seed phrase' recovery option. Common attacks target seed phrases through phishing (fake support asking for your phrase), malware (clipboard hijacking), and physical theft. Hardware wallet manufacturers recommend metal seed phrase backups that survive fire and water damage.
A seed phrase (recovery phrase or mnemonic phrase) is a sequence of 12-24 words generated when you create a cryptocurrency wallet, serving as the master key that can reconstruct all private keys and access all funds across all addresses in that wallet. The words come from a standardized list of 2,048 English words (BIP-39 standard), and their specific order encodes a large random number that deterministically generates your entire wallet hierarchy. Losing your seed phrase means permanent loss of access to your funds — there is no recovery mechanism, no customer support, and no reset option. The irreversible nature of seed phrase loss has resulted in an estimated $140+ billion in permanently inaccessible Bitcoin alone. Storage best practices include: writing on durable material (metal seed plates resist fire and water), never storing digitally, keeping in a secure physical location, and considering geographic distribution (storing copies in different secure locations).
A Bitcoin holder who stored his seed phrase on a hard drive that ended up in a landfill in Wales lost access to 7,500 BTC (worth $500M+) — he's been petitioning the city council to excavate the landfill since 2013.
No legitimate entity will ever ask for your seed phrase — not customer support, not wallet companies, not blockchain foundations. Anyone asking is attempting to steal your funds. Your seed phrase should never be entered into any website, shared with any person, or stored on any internet-connected device. This is the number one rule of crypto security.