ICAO 9303

ICAO 9303 is why a border officer in one country can read a passport issued by another. It specifies the two lines of monospaced text at the bottom of the data page, the card layouts, and the chip inside the cover, in enough detail that a reader built by one party works on documents issued by any other.

The machine-readable zone

The MRZ encodes name, document number, nationality, date of birth and expiry in a fixed layout with check digits. The check digits are the useful part: a misread digit usually fails arithmetic rather than passing as a different, plausible person. That property is what makes an MRZ read something a machine can accept without a human looking at it.

The chip, and what it actually proves

A modern passport carries a contactless chip holding a signed copy of the same data. Passive authentication verifies that signature against a country's certificate. Done properly it is stronger evidence than optical reading, because it detects a substituted photograph or an altered field. Done against certificates you generated yourself, it proves the plumbing works and nothing about a real document.

Why an identity product cares

Nearly every high-assurance identity check in the world starts by reading one of these documents. A verification product that cannot read them accurately is not competing; the standard is the floor, not the differentiator.