Machine-readable zoneMRZ

The two or three lines of code at the bottom of a passport.

The lines look like rows of letters, numbers, and arrows, and a machine can read them in an instant to get the holder's name, document number, and dates.

A block of text encoded to Document 9303, the travel document standard from the International Civil Aviation Organization (ICAO), with check digits calculated over key fields such as the document number, date of birth, and expiry date.

The zone comes in a few sizes, depending on the document:

• Passports carry two lines of 44 characters each.
• Identity cards typically carry three lines of 30 characters each.
• Some smaller travel documents carry two lines of 36 characters each.

Check digits make errors detectable:

1. The standard assigns each character a value.
2. It multiplies the values by a repeating set of weights and adds them up.
3. The result, reduced to a single digit, is printed as the check digit.
4. A reader repeats the math, and a mismatch shows that a character was misread or altered.

The machine-readable zone sits next to terms that are easy to mix up:

• Optical character recognition (OCR) is the technology that reads the zone from an image.
• NFC chip reading reads the electronic chip, and the zone data is often used to unlock it.
• Government-issued ID is the document the zone belongs to.

For more, see What is a Biometric Passport or e-Passport?