An MRZ is a coded zone that is used on identity documents like passports, ID cards and sometimes even driving licenses. MRZ stands for machine readable zone. It is an international standard (ICAO 9303) developed by governments, customs offices and airlines. It is a way of securely compacting identity document information into a coded string of characters that a computer system or smartphone camera can read. Almost all passports are nowadays fitted with an MRZ.
An MRZ consists of two or three strings of characters, checksum numbers and separators on the front of passports or the backside of ID cards. For the string a special font called OCR-B is used. This font is specifically developed to make it easier for computers to read and prevent reading errors as much as possible. The checksum numbers are used to validate the extracted data that is in the MRZ and is a safety measure against fraude.