TL;DR: Error correction in QR codes helps maintain readability even with damage or distortion.

Technical explaination

Error correction is a built-in feature of QR codes that allows them to remain readable even when partially damaged, dirty, or distorted.

This is achieved through Reed-Solomon error correction, which adds redundant data to the QR code during its creation.

This extra data helps the QR code scanner reconstruct the original information, ensuring a successful scan despite imperfections.

Error correction levels QR code example
This is where the error correction levels are stored in the QR code

Error Correction Levels

QR codes offer four different error correction levels, each providing a varying degree of protection against damage. These levels are:

  • Low: This level provides the least amount of error correction, allowing for up to 7% of the QR code's data to be restored if damaged.
  • Medium: With this level, up to 15% of the QR code's data can be restored, offering a moderate level of error correction.
  • High: This level allows for up to 25% of the QR code's data to be restored, providing a higher level of error correction.
  • Best: Offering the highest error correction level, this level can restore up to 30% of the QR code's data if damaged.

Each error correction level has its advantages and drawbacks. Lower levels result in smaller QR codes with less data, making them easier to scan and quicker to generate.

However, they offer less protection against damage. On the other hand, higher levels provide greater protection against damage but result in larger, more complex QR codes that may require a higher resolution scanner or a closer scanning distance.

Simple explanation

When you're QR code is damaged the Error Correction makes sure your QR code is still readable, depending on the damage and the level of Error Correction you choose.

For example: If you choose an Error Correction level of 25%, a quarter of your QR code can be damaged or replaced by a Logo, and your phone will still be able to read it.

Damaged QR Code

It doesn't mean (like the example above) that you can remove 25% of the bottom. Since the position markers always have to be visible. But you could add a logo in the center of the QR code.

Make sure the Position Markers are always visible since they determine the boundaries of the QR code so the phone can read the information inside of the QR code.