What is MRZ?

MRZ stands for Machine Readable Zone — the block of standardised text printed at the bottom of passports, ID cards, and visas. The format is defined by ICAO 9303, a standard issued by the International Civil Aviation Organization that ensures every country encodes the same fields in the same positions.

The MRZ is printed in OCR-B, a font designed for machine reading where every character occupies exactly the same width. That fixed spacing lets scanners divide each line into equal slots and read characters reliably, which is why OCR-B is used for the MRZ even when the rest of the document uses a different typeface.

What data is encoded

Each MRZ line encodes specific fields: document type, issuing country, document number, surname, given names, nationality, date of birth, sex, expiry date, and optional data. Dates are written as YYMMDD, so 12 July 1942 becomes 420712.

Several fields are followed by a check digit — a single character calculated from the field value using a weighted algorithm defined in ICAO 9303. A composite check digit covers multiple fields together. These digits let any reader detect transcription errors or document tampering without external databases.

MRZ layouts by document type

Each document type defines how many lines the MRZ contains and how many characters each line holds. The diagrams below show the field positions for each format.