Passports must carry an optically variable device, ICAO says

What you see

Turn a modern passport's photo page under a light and tilt it, and part of the printed pattern shifts color or reveals a hidden image, a security feature, not a decorative one. ICAO Doc 9303, Part 2, the standard for the security design of machine-readable travel documents, requires this: it defines "the interference characteristic of a hologram or other optically variable device that can be uniquely identified by a suitable reader" as one recognized category of machine-verifiable security feature. What a border officer or a reader machine sees is a controlled optical effect that changes with viewing angle, checked against a known pattern, not an image floating free of the page.

How it works

Doc 9303 does not mandate one single optical technology; it names a family of "optically variable features," including "optically variable ink (OVI)" and "diffractive optically variable image devices (DOVIDs)" that can be laser-personalized so a secondary image, invisible under one light source, becomes visible under another. The standard states that where a document is made entirely of plastic, "optically variable security features shall be employed" as high-grade features or equivalent devices. The mechanism relies on diffraction gratings or thin-film interference structures embossed or printed onto foil or ink, engineered so the reflected color or image depends on the angle of illumination, the same optical principle used in security holograms generally, a verification tool rather than a picture.

Viewing conditions and limits

These features are checked two ways: visually, by a person tilting the document under ordinary light, and mechanically, by a reader comparing the feature under controlled illumination against an expected pattern. The standard recommends combining an optically variable feature with other measures such as laminate protection and personalized secondary images, rather than relying on any single feature alone. ICAO's Traveller Identification Programme page, retrieved 16 September 2026, frames Doc 9303 within a broader five-element identity strategy covering evidence, issuance and inspection systems.

What it is not

Doc 9303's optically variable devices are not free-space or volumetric holograms of the kind shown in a display; they are thin, reflective security foils and inks designed to defeat photocopying, verified by angle-dependent color shift rather than by reconstructing a scene a viewer walks around. The standard, now in its Eighth Edition, is periodically revised, so any description reflects the material as retrieved on 16 September 2026.

• Which edition of Doc 9303 does a given passport claim to follow, and has that edition been superseded?
• Is the optically variable feature on a document a genuine diffractive structure, or a cheaper printed color-shift imitation?
• Does the issuing authority combine the device with the other layered features the standard recommends, or rely on it alone?

Doc 9303 is a useful anchor for the word hologram in security because it refuses to treat the word as self-explanatory: it defines the feature by what it does, an interference or diffraction effect a reader or a human eye can check, rather than by branding. That is the same discipline this site applies to every other display calling itself a hologram.