QR Code Best Practices: Size, Error Correction and Scanning

A QR code only works if people can scan it. This guide covers the practical decisions that determine whether a code scans reliably: size, print versus screen use, quiet zones, contrast, error correction and testing.

Size: screen versus print

A code on a screen can be small because someone holds the phone close. A code on a poster must be larger because it is scanned from farther away. As a rough rule of thumb only, the minimum physical size is about the scanning distance divided by ten: a code meant to be scanned from one meter away should be at least about ten centimeters across. This is not an ISO requirement, and actual readability depends on the QR code version, module size, scanner and device, contrast, lighting, print quality and surrounding conditions.

For downloadable codes from our generator:

• 512 px — suitable for viewing on a screen.
• 1024 px — better for printing or scanning from across a room.

Quiet zone

Leave a blank border — the quiet zone — around the code, at least four modules wide on every side. Do not crowd the code against the edge of a design, and do not place text or logos inside it.

Contrast

Use a dark code on a light background. Black on white is the most reliable combination. Do not invert the colors, and avoid low-contrast pairs such as light gray on white — scanners need a clear difference between the dark modules and the background.

Error correction

Error correction lets a damaged or partially covered code still scan. There are four levels — L, M, Q and H — recovering roughly 7, 15, 25 and 30 percent of the code's data respectively. The higher the level, the more damage the code can survive, but the larger and denser the code becomes.

• Medium (M) — a good default for clean, on-screen codes.
• High (H) — choose this for printed codes that might get scuffed, folded or partly covered by a logo.

Test before you print

Print the code at its actual size and scan it with more than one phone, from the distance and angle people will actually use. Check that the destination link loads and works on a mobile device. A code that looks perfect on screen can fail once printed.

Placement

• Put the code on a flat surface, not a curved one.
• Position it at about eye level, in good light.
• Keep it away from folds, edges and corners where it can tear.
• Do not put a QR code on something that moves.

Common mistakes

• Making the code too small for the scanning distance.
• Using low contrast or inverted colors.
• Leaving no quiet zone around the code.
• Linking to a page that is not mobile-friendly.
• Not telling people what the code is for.

When not to use a QR code

A QR code is not always the right tool. Skip it when your audience is unlikely to scan, when a short typed web address is simpler, in poorly lit locations, or for anything security-sensitive where you do not want people scanning a code they cannot inspect first.

Static versus dynamic QR codes

A static QR code encodes the information directly in the pattern, so it cannot be changed after it is created. A dynamic QR code encodes a short redirect URL instead, so the destination can be updated later without reprinting the code — but it requires an external service to host the redirect, and the code will not work if that service goes down.

The QR tools on this site create static QR codes: whatever you enter is encoded into the image itself, with no external service and no redirect. If you need to change the destination later, you must create and print a new code.

Which tool to use

Create the code that matches what you want to share:

• Any text or link: QR Code Generator
• A web address: URL to QR Code
• Guest Wi-Fi access: WiFi QR Code Generator