How do crypto QR codes work?

A crypto QR code is a square barcode that holds a wallet address or a full payment request, so you can scan it instead of typing a long string. A wallet app reads the image, turns it back into text and fills in the send screen for you to approve.

What is inside a bitcoin QR code?

The simplest bitcoin QR code contains only an address. Many wallets instead encode a payment link in the format set out in BIP-21, a Bitcoin standard written for links and QR codes. It starts with "bitcoin:" followed by the address and can add optional fields:

• amount, written in BTC with a period as the decimal point
• label, a name for the recipient
• message, a note describing the payment

Fields that begin with "req-" are mandatory, so a wallet that does not understand one must reject the whole request. BIP-21 also says wallets must not act on a link without the user's permission. As of October 2026, the BIP-21 page lists it as closed and replaced by BIP-321, which updates the same scheme. Lightning payments use their own format, covered in what is a Lightning invoice.

How does a crypto QR code payment work on Ethereum?

Ethereum wallets follow ERC-681, a final standard modeled on the bitcoin: format. Its links start with "ethereum:" and can name the recipient address or an ENS name, a chain ID for the network, and a value in wei, the smallest unit of ether. For token payments, the link can point to a token contract's transfer function with the recipient and amount as parameters. ERC-681 treats amounts as suggestions the user can change.

Our guide on how to send and receive crypto covers the basic steps.

How do QR code scams target crypto users?

A QR code hides its contents until it is scanned, which makes it useful to scammers. The FTC has described a pattern in which someone posing as a government official, utility, romantic partner or prize promoter pressures a victim to withdraw cash and feed it into a crypto ATM. The scammer then sends a QR code with their own address embedded, and the crypto bought goes straight to them. The FTC says real agencies and utilities never ask for payment in crypto. More detail is in how crypto ATM scams work.

In a December 2023 alert, the FTC also warned that scammers paste fake QR codes over real ones in public places and send codes by text or email with urgent excuses. These can lead to login-stealing sites or malware.

How can you check a crypto QR code before paying?

After scanning, wallets show the decoded address, network and amount. Comparing the first and last characters of the address with one you got from a trusted source, and confirming the network and token, helps catch a swapped code. ERC-681 itself advises that payment links should come only from authenticated sources, since a crypto transaction usually cannot be reversed.