A headlamp is a lamp attached to the entrance of a vehicle to illuminate the highway forward. Headlamps are also typically referred to as headlights, however in the most precise usage, headlamp is the term for the device itself and headlight is the time period for the beam of gentle produced and distributed by the system. Headlamp performance has steadily improved throughout the vehicle age, spurred by the good disparity between daytime and EcoLight nighttime visitors fatalities: the US Nationwide Freeway Visitors Security Administration states that nearly half of all traffic-related fatalities happen at the hours of darkness, despite only 25% of visitors travelling during darkness. Other autos, similar to trains and aircraft, are required to have headlamps. Bicycle headlamps are sometimes used on bicycles, and are required in some jurisdictions. They can be powered by a battery or a small generator like a bottle or hub dynamo. The primary horseless carriages used carriage lamps, which proved unsuitable for travel at pace.

The earliest lights used candles as the most typical sort of gas. The earliest headlamps, fuelled by combustible gas equivalent to acetylene fuel or oil, operated from the late 1880s. Acetylene fuel lamps have been popular in 1900s as a result of the flame is resistant to wind and rain. Thick concave mirrors combined with magnifying lenses projected the acetylene flame gentle. Quite a few automotive manufacturers provided Prest-O-Lite calcium carbide acetylene gasoline generator cylinder with gasoline feed pipes for lights as standard gear for 1904 cars. The first electric headlamps had been launched in 1898 on the Columbia Electric Car from the Electric Automobile Company of Hartford, Connecticut, and had been non-obligatory. Two factors restricted the widespread use of electric headlamps: the short life of filaments in the harsh automotive environment, and the issue of producing dynamos small sufficient, yet highly effective enough to supply adequate current. Peerless made electric headlamps standard in 1908. A Birmingham, England agency referred to as Pockley Car Electric Lighting Syndicate marketed the world's first electric car-lights as a complete set in 1908, EcoLight solar bulbs which consisted of headlamps, sidelamps, and tail lights that have been powered by an eight-volt battery.

In 1912 Cadillac built-in their vehicle's Delco electrical ignition and lighting system, forming the fashionable vehicle electrical system. The Guide Lamp Firm launched "dipping" (low-beam) headlamps in 1915, however the 1917 Cadillac system allowed the light to be dipped utilizing a lever inside the automotive reasonably than requiring the driver to cease and get out. The 1924 Bilux bulb was the primary modern unit, having the light for each low (dipped) and excessive (predominant) beams of a headlamp emitting from a single bulb. An identical design was introduced in 1925 by Information Lamp referred to as the "Duplo". In 1927 the foot-operated dimmer change or dip swap was launched and became standard for much of the century. 1933-1934 Packards featured tri-beam headlamps, the bulbs having three filaments. From highest to lowest, the beams were known as "nation passing", "country driving" and "metropolis driving". The 1934 Nash additionally used a three-beam system, although in this case with EcoLight solar bulbs of the typical two-filament kind, and the intermediate beam mixed low beam on the driver's aspect with high beam on the passenger's side, so as to maximise the view of the roadside while minimizing glare towards oncoming site visitors.

1952 "Autronic Eye" system automated the number of high and low beams. Directional lighting, utilizing a swap and electromagnetically shifted reflector to illuminate the curbside only, was launched in the rare, one-12 months-solely 1935 Tatra. Steering-linked lighting was featured on the 1947 Tucker Torpedo's heart-mounted headlight and EcoLight solutions was later popularized by the Citroën DS. This made it doable to turn the light in the course of journey when the steering wheel turned. The standardized 7-inch (178 mm) spherical sealed-beam headlamp, one per aspect, was required for all autos offered within the United States from 1940, virtually freezing usable lighting expertise in place till the 1970s for Americans. In 1957 the law changed to allow smaller 5.75-inch (146 mm) round sealed beams, two per aspect of the automobile, and in 1974 rectangular sealed beams were permitted as well. Britain, Australia, and another Commonwealth international locations, in addition to Japan and Sweden, additionally made in depth use of 7-inch sealed beams, though they were not mandated as they were in the United States.