Colourful QR Codes: Which Colours Still Scan (and Inverted QR Codes)

Colorful QR codes can scan well, as long as they have strong contrast. A QR code scanner does not read colour. It reads how bright the dark and light parts are. So blue on white or navy on cream can work, because the dark parts are much darker than the light parts.

The safe rule is a dark code on a light background, with a blank margin around it. Inverted codes, with light modules on a dark background, work on some scanners but not all. This guide explains which colours still scan, which to avoid, and how to test your code before you print it.

The Short Answer: Dark on Light

• Dark modules on a light background. Choose a dark colour for the code and a light colour for the background.
• Strong contrast. The dark parts should be much darker than the light parts, because scanners look at brightness, not colour.
• Be careful with inverted colours. Some scanners read light-on-dark codes and some do not. Dark on light is the safest choice.

How Scanners Read QR Codes

When designing colourful QR codes, it's important to remember that scanners don’t care about the actual colours used. Instead, they focus on the contrast between the dark and light areas of the code. The dark modules, which are the ones that contain the data, need to stand out clearly against the light background.

To ensure your QR code scans reliably, use a contrast checker to verify that the contrast ratio is high enough. A common rule of thumb is to aim for a contrast ratio of at least 4:1 between the dark and light areas, though a higher ratio will make the code more reliable. For example, a navy blue QR code on a cream background can work well if the navy is significantly darker than the cream.

Before finalizing your design, test the QR code to make sure it scans correctly. This step is crucial to ensure that your colourful QR code remains functional and reliable.

Colours to Avoid

When creating colourful QR codes, it's important to avoid certain colour combinations to ensure they scan reliably. Here are the key colours and combinations to avoid:

• Light on Light: Using light colours on light backgrounds, such as yellow on white or light grey on white, can result in low contrast. This low contrast often causes scanning issues because the QR code lacks the necessary definition for a scanner to read it accurately.

• Similar Brightness Levels: Two colours that look different to the human eye but have similar brightness levels can also cause problems. For example, red on green or orange on red might appear distinct to us but can be indistinguishable to a QR code scanner. This similarity in brightness can lead to scanning failures.

• Complex Backgrounds: Avoid using gradients, patterns, or photos behind the QR code. These can hide the QR code modules, making it difficult for the scanner to read the code accurately. Similarly, a busy or textured background can reduce the reliability of the QR code.

By avoiding these problematic colour combinations and backgrounds, you can ensure your QR codes remain both visually appealing and reliable.

Inverted QR Codes

An inverted QR code has light modules on a dark background. Some phone cameras and apps can read them. Older phones, older scanner apps and some dedicated barcode scanners may not.

If you use one, test it on several phones and scanner apps before printing. The safest choice is a normal dark-on-light code.

Quiet Zone and Printing

Denso Wave, the inventor of the QR code, says: "QR Code requires a four-module wide margin at all sides of a symbol." Keep that margin blank and light, even when the code itself is coloured.

Denso Wave also recommends printing QR codes "as large as possible within the available printing area."

Screens and print show colours differently, so do not rely on the screen preview. Print a test copy and scan the printed code before you print a large batch.

Practical Steps for Reliable QR Codes

1. Pick a dark colour for the code, such as navy, dark green, deep purple or black, and a light colour for the background.
2. Keep the blank margin around the code.
3. Keep the background behind the code plain. Do not put gradients, patterns or photos behind it.
4. Test the code with the Camera app on at least one iPhone and one Android phone, in normal light and from a normal distance.
5. If a coloured code is not reliable, go back to black on white.

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Frequently Asked Questions

What is the best color for a QR code?

A dark colour for the code on a light background. Scanners read brightness differences, not colour, so dark on light is the most reliable.

Can QR codes be inverted?

Some scanners can read inverted codes (light on dark) and some cannot. Older phones, older scanner apps and some barcode scanners may fail, so dark on light is safer. Test an inverted code on several phones first.

How do I test a QR code?

Scan it with the Camera app on at least one iPhone and one Android phone, in normal light and from a normal distance. Test the printed copy, not only the screen preview, before you print a large batch.

What is the quiet zone in QR codes?

The quiet zone is the blank margin around the code. Denso Wave, the inventor of the QR code, says it must be four modules wide on all sides. Keep it light, even if the code is coloured.

Why do QR codes need high contrast?

Scanners read the difference in brightness between the dark and light parts. If the two are too similar, the scanner cannot tell the modules apart.

Can I use gradients or patterns behind a QR code?

It is best not to. Gradients, patterns or photos behind the code can hide the modules and make it less reliable. Use a plain background.

How do I check the contrast ratio of a QR code?

Use a contrast checker tool. A common rule of thumb is a contrast ratio of at least 4:1 between the dark and light parts, and higher is more reliable. It is a guideline from QR guides, not an official test.

What is the recommended size for printing QR codes?

Denso Wave recommends printing QR codes as large as possible within the available printing area. Keep the blank margin around the code, and test a printed copy on different phones.

Why do some QR codes fail to scan?

Common causes are low contrast, dark and light colours with similar brightness, and a busy background that hides the modules. Use dark modules on a clearly lighter, plain background.

Which colour combinations should I avoid?

Avoid light colours on a light background, such as yellow on white, and pairs that look different but have similar brightness, such as red on green. Scanners read brightness, so these often fail. Also avoid gradients, patterns or photos behind the code.