Private key
A secret cryptographic code that gives full and exclusive control over the funds recorded at a given blockchain address.
A private key is a unique, mathematically generated string of characters that unambiguously proves the right to control the cryptocurrency assigned to a specific address. Whoever holds the private key actually controls the funds — regardless of whose wallet it formally is.
Hence the popular industry saying "not your keys, not your coins" — when you hold cryptocurrency on an exchange, you don't own your private keys, you're just trusting that the exchange properly manages its own. Losing or leaking a private key means, in practice, an irreversible loss of funds, so it should never be shared with anyone or entered on suspicious websites.
Related terms
Seed phrase (recovery phrase)
A sequence of 12-24 random words from which all of a wallet's private keys can be restored.
Crypto wallet
A tool for storing the private keys you use to manage the cryptocurrencies recorded on the blockchain.
Cold wallet vs. hot wallet (offline and online wallets)
A hot wallet is connected to the internet and convenient for everyday use; a cold wallet stores keys offline and is safer for larger amounts.