People often use nightlights for the sense of security which having a light on provides, or to relieve fear of the dark, especially in young children. Nightlights are also useful to the general public by revealing the general layout of a room without requiring a major light to be switched on, for avoiding tripping over stairs, obstacles, or pets, or to mark an emergency exit. Exit signs often use tritium in the form of a traser. Homeowners may place nightlights in bathrooms and kitchens to avoid turning on the main light fixture and causing their eyes to adjust to the light.
Some frequent travelers carry small nightlights for temporary installation in their guestroom and bathroom, to avoid tripping or falls in an unfamiliar nighttime environment. Gerontologists have recommended use of nightlights to prevent falls, which can be life-threatening to the elderly. The low cost of nightlights has enabled a proliferation of different decorative designs, some featuring superheros and fantastical designs, while others feature the basic simplicity of a small luminous disc.
Early electrical nightlights used small incandescent lamps or small neon lamps to provide light, and were much safer than small candles using an open flame. The neon versions consumed very little energy and had a long life, but had a tendency to flicker on and off (reminiscent of a candle), which some users liked and others found annoying. In the 1960s, small nightlights appeared that featured a low-powerelectroluminescent panel emitting soft green or blue light; similar lights are still available today.
Some nightlights include a photocell, which enables them to switch off when the ambient light is sufficiently bright. Other designs also feature a built-in passive infrared sensor to detect motion, and only switch on when somebody is passing by in the dark. With the availability of low-cost LED, many different variants have become available, featuring different colors, sometimes changing automatically or in a user-controllable way.