Why does the side view mirror on your car say "objects in mirror are closer than they appear"?

The given phrase is a kind of safety warning which is required to be engraved on the passenger side mirrors of the motor vehicles in the countries like the United States, Nepal, India, Canada, and Saudi Arabia.

It is printed on the mirror because while the mirror on the vehicle is not a plane mirror. It is a conves mirror which gives a useful field of the view. The mirror makes the objects appear smaller.

The smaller-appearing objects seem away than in actual, a driver might make the maneuver such as the lane change assuming the adjacent vehicle is the safe distance behind, when in fact the vehicle is quite closer. Thus, the warning serves as the reminder to driver of the potential accident or hazard.