What aspect of an ID indicates that it was issued to someone under 21?

The identification being vertical is a standard practice in many jurisdictions to signify that the holder is under the age of 21. This visual distinction helps various establishments quickly determine the age of the individual, particularly in contexts where age verification is critical, such as when purchasing alcohol or entering age-restricted venues. The vertical format is distinct and easily recognizable as a means of protecting minors from accessing materials or environments intended for an older audience.

In contrast, options such as holograms, passport attachments, or gold seals do not consistently indicate age restrictions across various forms of identification, making them less reliable for this specific purpose. The vertical orientation serves as a clear and straightforward indicator recognized widely by both the public and law enforcement, ensuring effective age verification.