A private key is a long string of letters and numbers that acts as the password to your cryptocurrency. It is generated when you create a crypto wallet and is mathematically linked to your public address. While your public address can be shared freely so others can send you funds, your private key must be kept completely secret.
Whoever holds the private key has full control over the associated funds. This is why the crypto community often says: "Not your keys, not your coins." If someone gains access to your private key, they can transfer all of your assets with no way to reverse the transaction.
Important rules for managing private keys:
- Never share your private key with anyone, including support staff or online forms.
- Store it offline whenever possible, such as on a hardware wallet or written on paper in a secure location.
- Make backups – Losing your private key means losing access to your funds permanently.
- Use a seed phrase – Most modern wallets generate a seed phrase that can restore your private keys if needed.
When you use a custodial exchange like Coinbase or Binance, the exchange holds the private keys for you. Non-custodial wallets like MetaMask put you in full control.
For a deeper look at protecting your crypto, read our wallet security guide.