What Is ZIP CRC?

CRC is the abbreviation of cyclic redundancy check. This check is used to create a calculation of all the data inside a compressed file. The CRC value is calculated whenever a file is added to an archive. When the archive id decompressed again, the program calculates the CRC value again and compares both values. If there is a difference in between the two values, a CRC error message is typically displayed, indicating that the extracted file does not match the originally zipped file. This happens when the archive and thus the compressed files inside were damaged. Even when only one of the files inside an archive is damaged this error can occur.

The CRC value itself does not say anything about whether the file is damaged or not. Thus, when you check the metadata of your archive or compressed file and find a CRC, it does not mean that your archive is corrupted. It only shows this initially calculated CRC value.