This guide is for general information only and is not legal advice. Laws change — verify current rules with your state DOT or a licensed attorney before relying on this for any legal matter. Read full disclaimer.
California requires white lamp on the front, visible from a distance of 300 feet to the front and from the sides of the bicycle. For the rear, red reflector — or a solid or flashing red light with a built-in reflector — on the rear, visible from 500 feet when directly in front of lawful upper-beam headlamps. side reflectors are required on each side: white or yellow forward of center, red or white rear of center. pedal reflectors (white or yellow) are required on the front and back of each pedal, or equivalent reflective material on the rider's shoes or ankles. Side and/or pedal reflectors are also required. The rule applies whenever it is dark. See Cal. Veh. Code § 21201(d)–(e).
The cheapest way to stay legal in California is a USB-rechargeable front white light and a rear red light or reflector that meets the spec above. A $30 light set covers it.
California also requires reflectors beyond the core front and rear lights. New bikes from a US shop will already meet this; if you've stripped the reflectors off, replace them or add reflective tape on the frame and pedals.