What is paper wallet?

A private key or recovery phrase printed on paper, once promoted as a simple way to hold Bitcoin offline.

The idea was appealing around 2013: generate a key pair on an offline computer, print it, send coins to the address, and destroy the digital copy. No device to fail, no software to update, nothing online to hack. Several websites generated them, often with an attractive folding design.

The design is fragile in practice, and a hardware wallet has replaced it. The term still appears in older guides and in advice passed along secondhand, which is why it is worth knowing why it fell out of use rather than just being told not to do it.

How it works

A generator creates a private key and its corresponding address, then renders both, usually as text plus QR codes. Coins sent to the address are controlled by whoever holds the printed key.

Four failure modes did the damage.

The change problem. Bitcoin spends whole unspent outputs. Spending part of a paper wallet's balance sends the remainder to a change address, and early tools frequently sent that change somewhere the owner did not control. People who thought they were spending a fraction lost the rest.

Generation trust. Using a website to generate a key means trusting that site's code and the machine running it. Several generators were compromised, and some deliberately recorded the keys they produced.

Printers. Most printers cache documents, many are networked, and some store spooled jobs on internal storage. The printer becomes an unaudited copy of the key.

Physical decay. Thermal and inkjet output fades, paper burns and absorbs water, and a single copy in a single location is one accident away from gone.

A hardware wallet addresses all four. Keys are generated on the device and never leave it, change is handled correctly by the wallet software, the backup is a seed phrase you write rather than a printout, and the device signs without exposing the key.

Example

Illustrative case of the change problem. Someone holds 1 unit on a paper wallet and wants to spend 0.2. They import the key into a wallet application and send 0.2 to a merchant.

The transaction consumes the whole 1 unit as an input, pays 0.2 to the merchant, and returns 0.8 as change. If the application returned that change to an address in its own new wallet, the paper is now empty and the 0.8 lives wherever that application put it. If the person then discards the application without backing it up, believing the paper still holds the balance, the remainder is gone.

Why it matters when you buy

The relevance is at the point of moving funds off an exchange. Advice to print a key is outdated, and following it introduces risks that no longer need to be taken. A hardware wallet with a written seed phrase backup is the current baseline, and the setup steps are at Hardware wallet setup, with backup approaches at Seed phrase backup methods.

Related terms

• hardware wallet — the current standard
• seed phrase — the backup format that replaced it
• private key — what a paper wallet stores
• cold storage — the property it aimed at
• coin control — the mechanic behind the change problem
• air gapped wallet — offline signing done properly

Questions

Are paper wallets still safe if I made one years ago?

The coins are fine while nobody has seen the key. The risk is in spending from it. Sweep the whole balance into a modern wallet rather than making a partial spend.

Can I just write a seed phrase on paper instead?

Yes, and that is standard practice. The difference is that the seed backs a wallet that handles change correctly and generates keys on a device, rather than being the only copy of a single key.

Why did anyone recommend these?

Before hardware wallets were widely available, printing a key was a plausible way to get coins offline. The failure modes became clear through experience, and better tools replaced it.