A QR code (short for Quick Response code) is a two-dimensional barcode that stores data in a grid of black and white squares. Any modern smartphone camera can read it in less than a second — no special app required.
QR codes were invented in 1994 by the Japanese company Denso Wave to track car parts on a production line. Three decades later they have become the most popular way to move someone from the physical world (a poster, a menu, a package) to a digital destination (a website, a Wi-Fi network, a payment).
How a QR code works
When you scan a QR code, your phone's camera does three things:
- Detects the three large squares in the corners — those are finder patterns that tell software this is a QR code and how it is oriented.
- Reads the pattern of black and white modules between them. Each module is one bit of data.
- Decodes the bits using Reed–Solomon error correction, so the code still works even if up to 30% of it is damaged or covered.
The result is a string of text. If the string starts with https:// the phone opens a browser. If it starts with WIFI: the phone joins a network. If it is a vCard the phone offers to save a contact.
Static vs dynamic QR codes
This is the single most important concept to understand before you print a QR code on anything:
- Static QR code: the destination URL is baked into the code itself. You cannot change it. If the URL ever breaks, the printed code is dead.
- Dynamic QR code: the code points to a short redirect URL you own. You can change where it redirects at any time — and you get scan analytics for free.
If the code is going on business cards, product packaging, restaurant menus, billboards or anything else printed, use a dynamic QR code. The extra flexibility is worth it, and a small monthly fee is much cheaper than reprinting 10,000 flyers.
What can you put in a QR code?
A single QR code can store up to 4,296 alphanumeric characters, but in practice you rarely need that much. The most common use cases are:
- URL — a link to a website or landing page
- vCard — a digital business card (name, phone, email, address)
- Wi-Fi — instant network join without typing a password
- Email / SMS / Phone — pre-filled message or dial
- PDF / file — a downloadable document
- Payment — UPI, PayPal.me, Venmo, crypto address
- App Store / Google Play — auto-detect the operating system and send the user to the right store
Best practices for a scannable QR code
A QR code is only useful if it scans on the first try. Follow these rules:
- Minimum size: 2 cm × 2 cm (0.8 in) for hand-held scanning, 10 cm × 10 cm for a poster at 3 metres distance.
- Contrast: the code must be darker than the background. Dark on light is ideal; never invert to light on dark unless your scanner supports it.
- Quiet zone: leave at least four modules of empty space around the code.
- Error correction level H (30%) if you add a centre logo — otherwise the logo will break the code.
- Test on multiple phones before printing. iPhone, Android and older devices can behave slightly differently.
Creating a QR code in under 30 seconds
- Pick a type (URL, vCard, Wi-Fi, …).
- Paste or type the target.
- Customise colours, add a centre logo, pick a frame.
- Download as PNG or SVG, or let us host the dynamic redirect and track every scan.
You can try the full builder free on the homepage — no account needed to preview, accounts start at $0.99/month for a dynamic code with tracking.
Key takeaways
- A QR code is a 2D barcode read by any smartphone camera.
- Use a dynamic QR code whenever the destination might ever change.
- Keep the code at least 2 cm × 2 cm, high-contrast, with a quiet zone around it.
- Error correction level H lets you safely add a centre logo.
- Track scans with a dynamic code to measure what is actually working.