Is a QR Code still readable when some areas of are damaged or missing?

In general, yes. It depends on the error correction level, that is being set when creating a QR Code. Error correction ensures that the QR Code stays readable, even if the QR Code is partially damaged, covered or pixels are missing.

There are 4 different levels:

• Level L - up to 7%
• Level M - up to 15%
• Level Q - bis 25%
• Level H - up to 30% of the QR Code may be damaged to stay readable
  

The higher the error correction, the more the QR code can be missing/damaged, but the bigger is the size of the QR Code.

If you just have a black & white QR Code, the error correction level L is sufficient.

We recommend to always use the highest error correction level H for designer QR Codes, so you can maximize the size of your logo in the QR Code.