What Is a QR Code and How Do QR Codes Work? (2026)

You scan a QR code almost every day — on a restaurant menu, a payment terminal, a product box or a Wi-Fi sign. But what actually happens when your camera reads one of those little black-and-white squares? This guide explains what a QR code is, how QR codes work under the hood, what they can store, and how to create and scan them safely in your browser.

What is a QR code?

A QR code (short for "Quick Response code") is a two-dimensional barcode that stores data in a square grid of black and white cells called modules. It was invented in 1994 by the Japanese company Denso Wave to track car parts, because the older one-dimensional barcode could not hold enough information. Where a traditional barcode stores maybe 20 digits in a single row, a single QR code can hold thousands of characters in two dimensions.

That capacity — plus the fact that any modern phone camera can read one instantly — is why QR codes are now everywhere: links to websites, Wi-Fi credentials, contact cards, payment requests, event tickets and app-download links.

How do QR codes work?

A QR code is really a tiny map of 1s and 0s. Each black module represents a 1 and each white module a 0, and the scanner reads that binary pattern back into text. Several fixed parts of the grid make this reliable:

• Finder patterns — the three large squares in the corners. They tell the scanner "this is a QR code" and let it work out the orientation, so you can scan it upside down or at an angle.
• Alignment and timing patterns — smaller markers that help the scanner correct for curved surfaces and keep the grid lined up.
• Format and version information — strips of modules that describe the code's size and its error-correction level.
• Data and error-correction area — the rest of the grid, which holds your actual content plus recovery data.

When you point your camera at the code, the phone finds the three corner squares, maps the grid, reads the modules as binary, and decodes them back into the original text or URL.

Why QR codes still work when they are damaged

One of the cleverest things about QR codes is error correction. Using a mathematical technique called Reed–Solomon coding, a QR code stores redundant data so it can still be read even if part of it is dirty, scratched or covered. There are four levels: L (about 7% recoverable), M (about 15%), Q (about 25%) and H (about 30%). This is also why companies can place a logo in the middle of a QR code: at a higher error-correction level, the logo simply covers modules the error correction can reconstruct. The trade-off is that higher correction leaves less room for data, so the code becomes denser.

What can a QR code store?

A QR code can encode different kinds of data, and well-designed scanners recognise the type and offer the right action:

• A website URL — the most common use; scanning opens the link.
• Plain text — a note, a code, a serial number.
• Wi-Fi credentials — network name, password and security type, so guests can join without typing.
• Contact details (vCard) — name, phone and email that save straight to contacts.
• Email, phone or SMS — pre-filled messages.
• Payment information — many payment apps encode an account or invoice reference in a QR code.

The maximum capacity depends on the data type and version — up to roughly 7,000 digits or about 4,300 alphanumeric characters at the largest size, though in practice shorter content scans faster and more reliably.

Static vs dynamic QR codes

A static QR code encodes the data directly, so the content is fixed forever once printed. A dynamic QR code instead encodes a short redirect link that points to content you can change later — useful for marketing, because you can update the destination (and track scans) without reprinting the code. For a simple link, Wi-Fi share or contact card, a static code is all you need.

How to create a QR code

You do not need an app or an account to make a QR code. The free PAYATE QR Code Generator turns any URL or text into a downloadable QR code right in your browser — nothing is uploaded to a server. For the best results, keep the content short (a shorter URL produces a less dense, easier-to-scan code), keep good contrast with dark modules on a light background, leave the empty "quiet zone" margin around the code, and test it before you print at size.

How to scan a QR code safely

On most modern phones you simply open the camera app and point it at the code; a notification appears with the link or action. If your camera does not support it, or you have a QR code saved as an image, you can use the PAYATE QR Code Scanner to scan it live from your webcam or from an uploaded image. Because a QR code can hide any URL behind an innocent-looking square, treat them like links from a stranger: preview the URL before opening it, be wary of codes stuck over the original on parking meters or posters ("quishing"), and never enter passwords or card details on a page you reached only through an unexpected QR code.

QR codes vs barcodes

A classic barcode is one-dimensional: it stores data only in the width of its bars, so capacity is tiny and it must be scanned in the right orientation. A QR code is two-dimensional, holds far more data, can be read from any angle, and survives damage thanks to error correction. If you need a traditional retail barcode instead — EAN, UPC or CODE128 — you can generate one with the PAYATE Barcode Generator.

Key takeaways

A QR code is a two-dimensional barcode that stores data as a grid of black and white modules, with corner finder patterns for orientation and Reed–Solomon error correction so it still scans when partly damaged. It can hold a URL, Wi-Fi login, contact card or payment reference, and any phone camera can read it. To make one, use the free QR Code Generator; to read one from an image or webcam, use the QR Code Scanner — and always preview the link before you tap it.