The security of US identification documents relies on multiple physical and optical features:
​1.  Holographic Elements:​​ Utilize optical interference to create 3D effects, presenting a high barrier to duplication.
​2.  UV Fluorescent Printing:​​ Employs inks that fluoresce under specific ultraviolet wavelengths, creating covert security markers.
​3.  Embedded Security Threads:​​ Threads integrated during manufacture, potentially featuring microtext or holographic effects, detectable via transmitted light or specific viewing angles.
​4. Transmitted Light Watermarks:​​ Images formed by variations in paper density during substrate production, clearly discernible via backlighting.
​5.Machine-Readable Data (MRZ/MRDF):​​ Typically utilizes 1D/2D barcodes or magnetic stripes as data carriers, facilitating automated information retrieval and authentication.