The short answer
A QR code (short for Quick Response code) is a two-dimensional barcode made of black and white squares. It stores text, usually a web address, that a phone camera reads and turns into an action: open a website, join a WiFi network, save a contact, start a call or pay with UPI.
Unlike a normal barcode, which stores a short number in one direction, a QR code stores data both horizontally and vertically. That is why it can hold hundreds of characters in a small square and still be read from any angle.
Where QR codes come from
QR codes were invented in 1994 by Masahiro Hara and his team at Denso Wave, a company in the Toyota group, to track car parts in factories. Ordinary barcodes held too little data and had to be scanned one at a time in the right direction; the new code could be read quickly from any side.
Denso Wave chose not to enforce its patent, so anyone can create and read QR codes without paying a licence fee. The format became an international standard, ISO/IEC 18004, and spread to tickets, payments and advertising. When phone cameras learned to read QR codes without a separate app (iPhone in 2017, most Android phones soon after), they became part of everyday life.
How a QR code is built
Every QR code has the same parts. Knowing them helps you understand why some designs scan and others don't.
- Finder patterns: the three large squares in the corners. They tell the camera where the code is and which way up it is.
- Alignment pattern: a smaller square near the fourth corner (in all but the smallest codes) that helps correct for curved or tilted surfaces.
- Timing patterns: dotted lines between the finder patterns that set the grid size.
- Format information: a strip next to the finders that stores the error correction level and mask.
- Data modules: all the remaining squares, which hold your content plus error correction.
- Quiet zone: the empty margin around the code. The standard asks for four modules of blank space on every side.
The squares are called modules. The smallest QR code (version 1) is 21 × 21 modules; the largest (version 40) is 177 × 177. The more data you store, the more modules you need, and the smaller each one becomes when printed at the same size.
How much can a QR code hold?
At the largest size and lowest error correction, a single QR code can hold up to:
| Content | Maximum |
|---|---|
| Digits only | 7,089 |
| Letters and digits (upper case) | 4,296 |
| Any text or bytes | 2,953 bytes |
These are theoretical limits. A code that full needs to be printed large and scanned carefully. In practice, keep content short: a link under about 100 characters makes a clean, easy code. See QR code size for printing for how content affects print size.
Error correction: why a logo doesn't break the code
QR codes use Reed–Solomon error correction, the same idea used on CDs. Extra data is added so the code can still be read when part of it is dirty, damaged or covered. There are four levels:
| Level | Can recover about |
|---|---|
| L (low) | 7% of the code |
| M (medium) | 15% |
| Q (quartile) | 25% |
| H (high) | 30% |
Higher levels make the code denser, so use L or M for plain codes and H when you place a logo in the middle. Our QR code with logo tool switches to H automatically.
What can a QR code do?
The code itself only holds text. Phones recognise certain formats and offer an action:
- Website link: opens the page (URL QR code).
- WiFi login: offers to join the network (WiFi QR code).
- Contact card (vCard): offers to save the contact (vCard QR code).
- Phone number, SMS, email or WhatsApp: opens the right app with the details filled in.
- Calendar event and map location: adds the event or opens the map.
- UPI payment: opens a UPI app with the payee filled in (payment QR code).
- Plain text: shows the text on screen (text QR code).
Static and dynamic QR codes
A static code holds your content directly. It is free and never expires. A dynamic code holds a short link to a provider's server, which forwards scans to your content; you can change the destination and count scans, but the code stops working if the provider switches it off. Our guide static vs dynamic QR codes compares them in detail. Every code made on QR Code Haven is static.
Are QR codes safe?
A QR code is just text, so scanning one can't harm your phone by itself. The risk is where it sends you. Criminals sometimes stick fake codes over real ones on parking meters, posters and shop counters to steal payments or logins, a scam called quishing. Before you open a link, look at the address your camera shows. For payment codes, check the payee name in your UPI app. Our QR code safety scanner shows what a code contains and flags common warning signs, and How to spot a fake QR code explains the tricks to watch for.
How to make a QR code
- Open our free QR code generator.
- Choose the type (link, WiFi, contact, text…) and enter your content.
- Pick colors, a logo and a frame if you like. Keep dark dots on a light background.
- Check the "Scans well" badge, then download PNG, SVG or PDF.
- Test the printed code with two different phones before printing in quantity.
How to scan a QR code
Open your phone's camera and point it at the code; a link or action appears on screen. On a computer, use our online QR code scanner with a webcam or upload an image. How to scan a QR code covers iPhone, Android, screenshots and what to do when nothing happens.
QR Code is a registered trademark of DENSO WAVE INCORPORATED.
Frequently asked questions
What does QR stand for?
Quick Response. The code was designed to be read quickly by a scanner, from any direction.
Who invented the QR code?
Masahiro Hara and his team at Denso Wave, a Japanese company in the Toyota group, in 1994.
Do QR codes expire?
Static QR codes never expire because the content is stored in the pattern itself. Dynamic codes can stop working if the provider deactivates them.
Is it free to make a QR code?
Yes. The format is free to use, and static codes made here are free with no sign-up, no watermark and no scan limits.
Can a QR code contain a virus?
The code itself is only text. The danger is a link to a harmful website, so check the address before opening it.
What is the difference between a QR code and a barcode?
A barcode stores a short number in one direction. A QR code stores data in two directions, so it holds much more and can be read from any angle.