QR Code Error Correction Level

The error correction in a QR code is the algorithm that ensures its readability even when the QR code is damaged. QR code error correction works by adding extra modules to the QR code patterns. The error correction level of QR codes determines to what extent the damaged part of the code is recovered during scanning. To determine the error correction level of a QR code, it is necessary to examine the density of modules in the rows and columns of the QR code.

QR code with error correction prevents the QR code from resulting in an invalid QR code in case of damage or distortion. Error correction levels are four in total, which are denoted as low (L), medium (M), quartile (Q), and highest (H) levels. Each level's ability to recover data differs; various QR codes use a different error correction code level. Sectors especially use the highest correction level if there is a high probability of damage or dirt during QR code usage. However, using low-level error correction is sufficient if the probability of damage is low.

What is Error Correction in QR Code?

The error correction in a QR code is the algorithm that ensures its readability even when the QR code is damaged. It is implemented through the Reed-Solomon algorithm. Sometimes, QR codes get damaged, stained, or improperly printed, making reading difficult and even infeasible. However, the QR code error correction algorithm prevents it. The level of error correction varies in different QR codes. Some use a higher error correction level, especially those more likely to be damaged. However, a lower error correction level is used in QR codes with a lower probability of damage.

How Does QR Code Error Correction Work?

QR code error correction works by adding extra modules to the QR code patterns. The added modules contain duplicates of the information that had been inserted. QR code scanners read the QR codes by using additional modules. Error correction is designed to work even when QR codes are damaged. Scanners read QR codes even if they are stained, damaged, or printed with errors using the error correction algorithm.

What is the Error Correction Level for QR Code?

The error correction level of QR codes determines to what extent the damaged part of the code is recovered during scanning. There are 4 error correction levels: L (low), M (medium), Q (quartile), and H (highest) levels. Each error correction level differs in the percentage of data recovered within the QR code. A higher percentage error correction level recovers more data but requires the QR code to be larger in size. The 4 QR code error correction examples are listed below. 

Low level (L)

Low-level error correction is a level that recovers 7% of the data. It is used in QR codes with a low probability of damage or staining.

Medium level (M)

Medium-level error correction is a level that recovers 15% of the data. It is used in QR codes with a medium level of risk compared to level L.

Quartile level (Q)

Quartile-level error correction is a level that recovers 25% of the data. The level is higher than level M and is used in QR codes with a higher probability of partial damage or dirt.

Highest level (H)

Highest-level error correction is a level that recovers 30% of the data. It is the highest QR code error correction level used, particularly by sectors with a high risk of damage or dirt during QR code usage, and the recovery rate is very high. QR code is made by finding a high error correction QR code maker online.

Identify the Error Correction Level of the QR Code

To determine the error correction level of a QR code, it is necessary to examine the density of modules in the rows and columns of the QR code. The density increases as the error correction level QR code increases. The appearance of two QR codes with the same data but different error corrections differs according to the error correction level. It is understood that lower density corresponds to a lower correction level from the appearance of the QR code, while higher density corresponds to the highest correction level used.

Do Higher QR Error Correction Levels Lead to Slower Scans?

Higher QR error correction levels do not necessarily lead to slower scans. The modules in the rows and columns are denser, requiring a larger-sized QR code if QR codes are in the highest error correction level. There is a probability of encountering slower scanning times than other QR codes due to the larger size of QR codes in the highest error correction level in some cases. However, that is not always true. Scanning speed depends more on QR code quality and lighting conditions than error correction. QR codes with the highest error correction level are scanned quickly if the other factors are not an issue.