QR Code employs error correction to generate a series of error correction codewords which are added to the data codeword sequence which enable symbol to be read even if it is dirty or damaged. The QR code achieves powerful error-correction capability by using Reed-Solomon codes, a widely used mathematical error-correction method. Four levels of error correction are available, higher level has high capability of recovery. Table below shows error-correction levels and their approximate ability of error correction.
When selecting the level of error correction, environmental conditions as well as the desired size of the QR Code symbol need to be taken under consideration.
For example, Level Q (25% error correction) or H (30%) may be required for factories or other applications where the QR Code is likely to become dirty or damaged. For clean environments and codes containing a large amount of data, Level L (7%) may be selected. In general, Level M (15%) is most frequently used.
