Bicycle lighting serves to increase the visibility of the bicycle rider to others in dark conditions, i.e. to increase the rider's conspicuity and to enhance the ability of the rider to see, illuminating the way forward. Both reflectors and active lights are used to make the rider more visible, and many jurisdictions require one or more types of light to be fitted to bikes ridden at night. White light in the front, red lights in the back, with orange reflectors on the side is the most common setup. Many types of light sources are used for bicycle lights.

The earliest bicycle  lighting and motor-car lamps were often powered by acetylene gas, the medium calcium of carbide now almost unused except by cavers. The light they gave was very bright but because they needed to be cleaned after use, and that the burner blocked easily, they were somewhat temperamental, and the arrival of battery lamps from the late 1890s, was welcomed.[1]

Early battery lamps generally used a lead-acid battery, but these were replaced by self-contained dry cells; lamps became smaller and more reliable. At the same time dynamos were developed which generated energy from the bicycle's own movement. These were more practical, as storage density in batteries was at this time very low.

Not all jurisdictions required use of bicycle  lights  after dark. In the UK the law requiring use of rear lights was resisted by cyclists' groups on the grounds that it downplayed motorists' obligation to be able to stop well within the distance they can see to be clear.

Replaceable-cell battery lights had a renaissance on the invention of the alkaline battery, with a much higher storage density. Moulding techniques for plastics also improved, allowing lens optics to be refined at low cost thus making more efficient use of the light output. During the 1980s the lighting market became more globalised: in Europe, the French "Wonder Lights" and Ever Ready brands gradually disappeared in favour of American, Japanese and German products.

In recent times there have been many advances: exceptionally efficient dynamos; cheap high-output sealed-unit halogen lamps originally developed for decorative Bicycle lighting; improved storage density in rechargeable batteries driven by the computer industry; high-output light emitting diodes (LEDs); white LEDs; high intensity discharge (HID) lights crossing over from the automotive sector.