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What is cold storage?
Cold storage means keeping private keys on something never connected to the internet, such as an offline computer, a hardware wallet or paper. Transactions are signed offline and only the signed result is carried to an online device to send.
What it means for you
Keys offline cannot be taken by online attackers, but the medium can be lost, damaged or stolen. Losing it without a backup means losing the funds for good. Keep a tested backup in a second location, and test a small transaction before moving large amounts in or out.
A common mistake: “Coins in cold storage can't be lost.”
In fact: Offline keys are out of reach of online attackers, but SEC staff note the physical device or paper can be lost, damaged or stolen, which may mean permanent loss if there is no working backup.
How it works
The keys are created on a machine that never goes online. A watch-only copy on an online machine, built from the wallet's master public key, shows the balance and drafts an unsigned transaction. That file is carried to the offline machine by USB or similar, signed there, and carried back to be broadcast. The private keys never touch a networked device; only the unsigned and signed transactions cross the gap. A hardware wallet automates the same split between signing and sending.
Sources: bitcoin.org: Secure your wallet, Electrum documentation: Cold storage, Bitcoin developer guide: Wallets, SEC Office of Investor Education: Crypto asset custody basics for retail investors · checked 4 October 2026
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Educational content, not financial advice. Written by hand and checked against the source named above. Something wrong? Tell us and we reply within two business days.