ECC Level (1-4)

ECC stands for 'Error Correction Code'.
As a printed QR code in the wild may get damaged, you can ask the system to create a code which has more info in it, and therefore is more likely to be read correctly.
Set against that, a higher level ECC creates a code with more rows and columns which makes it more difficult to read if it is to be printed as a small square.
You can choose one of these 4 levels:

1 - Level L – up to 7% damage
2 - Level M – up to 15% damage
3 - Level Q – up to 25% damage
4 - Level H – up to 30% damage

This code is based on "Javascript QR Encoder", Copyright 2010, tz@execpc.com, released under GPLv3