What is the MRZ on a passport or ID card, and why hide it?
The two lines of code at the bottom of the photo page, decoded — and why to cover them on any copy.
Short answer
< characters at the bottom of a passport’s photo page, or three shorter lines on most ID cards. It follows the ICAO 9303 standard and encodes your name, document number, nationality, date of birth, sex and expiry date in a form any scanner can read instantly.- It repeats the most sensitive printed fields, so hiding the document number alone leaves them exposed.
- Cover every line with a solid box — a partly visible MRZ can still give up its structure.
- Redacting a copy does not change your real document: it still scans normally at a border or check-in desk.
Look at the bottom of your passport’s photo page, or the back of a national ID card, and you will see two or three lines of capital letters, numbers and < characters that look like a typo. That is the MRZ — the machine-readable zone — and it is the part of the document every one of our guides tells you to cover before sharing a copy. Here is what it actually is.
What the MRZ is
The MRZ is a standardised strip of text designed to be read by a machine, not a person. It follows ICAO Document 9303, the same international standard used for passports and many national ID cards worldwide, which is why a border scanner in one country can read a passport issued by another. Two lines on a passport (44 characters each), or three shorter lines on many ID cards — either way, the format is fixed and public, which means anyone with a basic reader — or a phone camera and free software — can decode it instantly.
- Cover before sharing
- Usually safe to leave visible
What information it encodes
Reading left to right, the MRZ packs in:
- Document type and issuing country.
- Your full name, exactly as printed on the document.
- The document number.
- Your nationality.
- Date of birth.
- Sex.
- Document expiry date.
- Check digits — extra characters a machine uses to confirm the other fields haven’t been tampered with.
In other words: almost everything a system needs to identify you, in a format built to be copied by software rather than typed by hand.
Why it matters more than the rest of the page
A printed name and photo tell a person who you are. The MRZ tells a machine — instantly, and at scale. That is exactly why it is the field most valuable to identity fraud: it is what automated systems for opening accounts, verifying age or registering a SIM card are built to read, and a clean photo of it copies with perfect accuracy. Hiding your document number and date of birth in the printed text but leaving the MRZ untouched defeats the point, since the MRZ repeats both — and more — in a form that’s even easier to lift.
How to hide it properly
A solid, opaque box over both (or all three) full lines is enough — partial redaction that leaves part of a line readable can still expose enough for the check-digit structure to be reconstructed. For the rest of the page — document number, date of birth, signature — and how to add a watermark on top, see how to redact a passport or ID card. Anonymize my ID covers the MRZ, and every other sensitive field, on-device in about a minute, with nothing uploaded.
Frequently asked questions
What is the MRZ on a passport or ID card?
MRZ stands for machine-readable zone: the two (on a passport) or three (on many ID cards) lines of capital letters, numbers and < characters printed at the bottom of the photo page or the back of the card. It follows a global standard (ICAO 9303), so any scanner or reader, anywhere, can pull your details from it automatically.
What information does the MRZ encode?
Your document type and issuing country, full name, document number, nationality, date of birth, sex, document expiry date, and check digits that let a machine verify the other fields weren't altered. It's a compact, complete summary of the identity data on the document.
Why should I hide the MRZ when I share a copy of my ID?
It's the single most concentrated piece of machine-readable identity data on the document — exactly what automated fraud and account-opening systems are built to read. A photo that hides everything except your name and face still proves who you are without handing over a ready-to-scan identity record.
If I cover the MRZ on a copy, does that stop my real document being scanned?
No — covering the MRZ on a redacted copy only affects that copy. Your physical passport or ID card is unchanged and scans normally at a border or check-in desk. Redaction protects copies you hand out, not the original document.