Those Weird Lines at the Bottom of Your Passport? They Know Everything.

Pop quiz: what’s the most dangerous part of your passport to leave unredacted?

If you said “the passport number” — close, but no.

It’s those two lines of gibberish at the very bottom of the data page. The ones that look like someone mashed a keyboard: P<ESPGARCIA<<MARIA<<<<<<<<<<<<<<<<<<<<<<<<. You’ve probably never thought twice about them. Most people haven’t.

They’re called the Machine-Readable Zone, or MRZ, and they’re basically your entire identity in a single, machine-parseable string.

What’s actually in there

Let’s decode an MRZ. Here’s what those two lines contain:

Line 1:

• Document type (P = passport)
• Issuing country (ESP = Spain)
• Your full surname and given names

Line 2:

• Passport number
• Nationality
• Date of birth
• Sex
• Passport expiry date
• A bunch of check digits (for error detection)

That’s right — your passport number, date of birth, nationality, and full name are all sitting there in a format that any OCR tool, any script, any half-decent programmer can parse in under a second. No need to “read” the document. Just scan the MRZ and you’ve got structured data.

Why this matters when you redact

Here’s the scenario: you’re a responsible person. Your landlord asks for a passport copy. You think “I should redact my passport number.” So you draw a nice black rectangle over the passport number field in the main data section. Feel good. Send it.

Except your passport number is still fully visible in the MRZ. Right there at the bottom of the same page you just “redacted.”

This happens all the time. People carefully redact the human-readable section and completely forget that the machine-readable section contains the same information. It’s like locking the front door and leaving the back door wide open.

A two-second test

Look at your passport’s data page. Find the two lines at the bottom. Now look for a sequence of 9 characters that matches your passport number. Found it? That’s what criminals find too.

How to actually redact your passport properly

When you redact a passport copy, you need to cover:

1. The passport number in the main data section
2. The entire MRZ — both lines, end to end
3. Your signature if visible
4. Any other field the recipient doesn’t need

Don’t try to surgically redact individual characters from the MRZ. It’s not worth the effort and you’ll miss something. Just cover both lines entirely.

The MRZ isn’t just on passports

You’ll find MRZ zones on:

• Passports (two lines, 44 characters each)
• National ID cards (three lines, 30 characters each)
• Visas (two lines, 44 characters each)
• Travel documents (refugees, stateless persons)

If a document has a machine-readable zone, it has your key personal data encoded in it. Every time.

One more thing

The MRZ is also what passport readers at airport gates use. It’s what NFC-enabled passport chips reference. It’s what border control systems scan. The MRZ is, by design, the most information-dense part of your document.

Which is exactly why it should be the first thing you redact when sharing a copy — not the last, and definitely not never.

Those weird lines at the bottom of your passport aren’t decoration. They’re your identity in plaintext. Treat them accordingly.