Error Correction Levels

 Error Correction Levels

QR Codes have an error correction capability where data can be restored even when substantial parts of the code are distorted or damaged.
These are maximum numbers, and the amount of text space available to you depends upon which of the four error correction schemes are used. The error correction algorithm is based upon Reed-Solomon, and comes in four correction levels.
1. Level L – 7% of characters can be restored (default)
2. Level M – 15% of characters can be restored (most often used)
3. Level Q – 25% of characters can be restored
4. Level H – 30% of characters can be restored
Level L and M are most suitable for codes found in clean environments where the code will not get damaged. Level Q and H are for dirty environments, as in manufacturing plants. The error correction level that you use will dictate the amount of text that can be encoded. For example, Level L will allow you to encode 4,296 characters, while Level H only allows for 1,852 characters.

The lower the error correction level, the less dense the QR code image is, which improves minimum printing size.
 The higher the error correction level, the more damage it can sustain before it becomes unreadable.
 Level L or Level M represent the best compromise between density and ruggedness for general marketing use.
 Level Q and Level H are generally recommended for industrial environments where keeping the QR code clean or un-damaged will be a challenge.