Passport Machine-Readable Zone (MRZ): Fields, Check Digits, and Chip

The passport machine-readable zone is the block of monospaced text at the bottom of your passport’s data page that border scanners read to pull your identity in seconds. On a standard passport book it runs two lines of 44 characters, printed in a font called OCR-B, and every position in those 88 characters has a fixed meaning defined by the International Civil Aviation Organization in Document 9303.1International Civil Aviation Organization. ICAO Doc 9303 Part 1 – Introduction That rigid layout is why the same scanner works in Tokyo, Toronto, and Tunis, and why a single smudged character can hold up a boarding line.

What the MRZ Looks Like

Three sizes exist, one for each type of travel document. A full-sized passport book uses the TD3 format: two lines of 44 characters.1International Civil Aviation Organization. ICAO Doc 9303 Part 1 – Introduction Mid-sized documents use TD2, with two lines of 36 characters.2International Civil Aviation Organization. ICAO Doc 9303 Part 6 – Specifications for TD2 Size Machine Readable Official Travel Documents Credit-card-sized documents like the U.S. passport card use TD1: three lines of 30 characters on the back of the card.3International Civil Aviation Organization. Machine Reading Options for TD1 Size MRTDs

Whatever the size, only 37 characters are allowed anywhere in the zone: capital letters A through Z, digits 0 through 9, and the less-than sign (<) used as a filler.[mfn]International Civil Aviation Organization. ICAO Doc 9303 Part 3 – Specifications Common to All MRTDs[/mfn] No lowercase letters, no punctuation, no accents. Characters print at exactly 10 per inch on a fixed-width grid, which is what lets an optical sensor tell one character from the next without ever guessing. When a field doesn’t use all its space, the leftover positions are packed with < signs, which is why the bottom of your passport page looks like a row of arrows.

Field-by-Field: What Every Position Means on a Passport

A TD3 passport packs your identity into 88 characters. Each position has a fixed job, and a scanner extracts your name, nationality, document number, and dates purely from where the characters sit on the line.4International Civil Aviation Organization. ICAO Doc 9303 Part 4 – Specifications for Machine Readable Passports

Line 1

  • Positions 1–2: document type. The first character is always P for passport. The second identifies the kind. Starting January 1, 2026, ICAO requires standardized two-letter codes: PP for an ordinary national passport, PD diplomatic, PO official or service, PE emergency, PR refugee travel document, PS stateless, PM military. Older U.S. tourist passports show P followed by a filler; they remain valid until they expire.5International Civil Aviation Organization. Harmonizing Document Type Two-Letter Code in Machine Readable Passports
  • Positions 3–5: three-letter code for the issuing country (USA, GBR, FRA).
  • Positions 6–44: holder’s name. Surname first, then two fillers (<<), then given names separated by single fillers, with < signs padding out to position 44. Anything past 39 characters is truncated.

Line 2

  • Positions 1–9: passport number.
  • Position 10: check digit for the passport number.
  • Positions 11–13: three-letter nationality code.
  • Positions 14–19: date of birth in YYMMDD format. March 15, 1985 prints as 850315.
  • Position 20: check digit for the date of birth.
  • Position 21: sex, coded F, M, or < for unspecified.
  • Positions 22–27: expiration date in YYMMDD format.
  • Position 28: check digit for the expiration date.
  • Positions 29–42: personal number or optional data assigned by the issuing country. Many countries leave this blank.
  • Position 43: check digit for the personal number field.
  • Position 44: composite check digit covering the passport number, both dates, the personal number, and their individual check digits together.

The two-digit year works in practice because passports don’t last more than ten years, and the expiration date gives the scanner enough context to place the birth year in the right century.

Why Your Name May Look Wrong

The 37-character set has no room for accents, apostrophes, hyphens, or non-Latin scripts, so ICAO defines strict conversion rules.6International Civil Aviation Organization. ICAO Doc 9303 Part 3 – Specifications Common to All MRTDs Hyphens turn into a single filler, so MARIE-ELISE reads MARIE

Names written in Cyrillic, Arabic, or other non-Latin scripts are transliterated into the available Latin letters using ICAO tables. Accented Latin letters usually lose their diacritics: é becomes E, and ö may become OE or just O depending on the country. Arabic uses X as an escape character, and Cyrillic letters map to combinations like ZH for Ж and KH for Х. Different countries sometimes transliterate the same letter differently, which is why the spelling on your Russian passport MRZ may not match the spelling on a visa issued elsewhere. That mismatch is a common trigger for secondary inspection even when nothing is actually wrong.

What the Check Digits Are For

Four check digits sit in Line 2. Three of them protect the passport number, date of birth, and expiration date individually. The fourth, at position 44, is a composite that runs across all of those fields and their individual check digits at once, so it catches errors that might slip through any single check, such as two fields being swapped.4International Civil Aviation Organization. ICAO Doc 9303 Part 4 – Specifications for Machine Readable Passports Each check digit is a mathematical fingerprint of its field, calculated by weighting every position on a repeating 7-3-1 cycle and taking the remainder after dividing by 10.1International Civil Aviation Organization. ICAO Doc 9303 Part 1 – Introduction If the scanner misreads one character, the arithmetic won’t line up and the system flags it.

A check digit mismatch does not mean the passport is fake. Worn printing, scratches, and scanning glare cause false flags all the time. The standard response is manual verification against the visual data page and, sometimes, secondary inspection.

How the MRZ Unlocks the Chip

Modern e-passports contain a contactless chip storing a digital copy of your biographical data and a facial photo. The MRZ is the key that opens it. Without physically reading the printed zone first, a scanner cannot access the chip, which is a deliberate defense against someone wirelessly skimming your passport through your bag.

The protocol is called Basic Access Control. The scanner reads the passport number, date of birth, and expiration date from the MRZ, each with its check digit, concatenates them into one string, hashes it with SHA-1, and uses the first 16 bytes of the result as the seed for two encryption keys. Scanner and chip then run a challenge-response exchange to prove they both derived the same keys, and only after that does the chip release its data. Everything from that point is encrypted. A newer protocol, PACE, uses stronger Diffie-Hellman key agreement but still derives its initial password from the same three MRZ fields.7International Civil Aviation Organization. ICAO Doc 9303 Part 11 – Security Mechanisms for MRTDs The printed zone is not just an immigration-line convenience; it is the cryptographic foundation for the biometric data on the chip.

What Happens If the MRZ Is Damaged

A scratch across the printed lines, water staining, or ink smearing can stop a scanner from reading the zone at all. Airlines are on the hook for fines if they board a passenger who is later refused entry, so gate agents tend to be cautious. If the MRZ looks compromised, they can refuse boarding even when the rest of the passport looks fine, and travelers denied boarding for a damaged passport generally have no right to a refund.

The U.S. Department of State treats a damaged passport as grounds for replacement. Qualifying damage includes water damage, significant tears, unofficial markings on the data page, missing visa pages, and hole punches. Ordinary wear, like a slight bend from a back pocket, does not require replacement.8U.S. Department of State. Frequently Asked Questions About Passport Services A damaged passport cannot be renewed by mail. You apply in person using Form DS-11, as if applying for the first time. For adults in 2026, the fees are $130 for the application plus a $35 acceptance facility fee, totaling $165 for a replacement book.9U.S. Department of State – Bureau of Consular Affairs. Passport Fees If you notice damage before a trip, applying for an expedited replacement is safer than betting on the gate scanner.