Headlight Legal: Is it illegal to put LED headlight in the car?

This is completely legal if the vehicle is equipped with LED headlights that comply with Federal Motor Vehicle Safety Standard (FMVSS NO.108) at the factory.
From October 31, 2023, Amazon US restricts the sale of light-emitting diode (LED) headlight modification kits because these modification kits do not comply with FMVSS NO.108. This means that most post-modification LED headlight kits are not allowed because they are not certified to relevant safety standards.
Tesla said it will adopt matrix LED headlights for consumers in the US market, indicating that in some cases, if automakers can ensure that their LED headlight technology meets the strict requirements of FMVSS NO.108, then it may be legal to use these advanced LED headlight technologies.

Headlight Laws: What You Need to Know

In the United States, each state has different regulations regarding the laws on driving. Here is a brief introduction to the regulations on the use of high beams and headlights. Drivers know that when road visibility is poor, turning on the high beams on the car is crucial to visibility, but if used improperly, it will bring danger to other vehicles because the high beams will dazzle the driver's eyes, making it difficult for the driver to see the road and causing accidents. Many states in the United States not only have unique rules for the correct use of headlights, but also have detailed regulations on what types of headlights can be installed, the color of the headlights, and the lampshades. Generally speaking, the regulations for the use of high beams in various states are: when approaching other vehicles at a distance of 200 feet (about 60 meters) to 300 feet (about 90 meters), the high beams must be dimmed.

It is important to know the laws of your state, province, or country before fully committing to using LED bulbs or headlights.

California

• RoHS regulations: California was one of the first states to pass the RoHS regulations, which limit the content of hazardous substances in electronic products, such as lead, cadmium, and mercury. As electronic products, LED headlights must comply with the restrictions on these hazardous substances.
  
• Energy efficiency labeling: According to 16 CFR Part 305, LED headlights must provide information such as lighting output, estimated annual energy consumption cost, lamp life, correlated color temperature, wattage, and design voltage on the label. California has strict implementation standards for this.

Illinois

• 
  RoHS regulations: Illinois has also passed similar RoHS regulations to limit the use of hazardous substances in electronic products. LED headlights must comply with these regulations when sold in the state.

New Jersey

• RoHS regulations: New Jersey also has strict RoHS regulations, requiring that the content of hazardous substances in LED headlights must be within the specified range.

Rhode Island

• RoHS regulations: Rhode Island also has similar regulations to limit the use of hazardous substances in electronic products, and LED headlights must comply with these requirements when sold in the state.

Wisconsin

• RoHS regulations: Wisconsin has passed RoHS regulations that strictly limit the content of hazardous substances in LED headlights.

Federal regulations

• 47 CFR Part 15: All LED headlights must comply with 47 CFR Part 15 to ensure that electronic devices that use radio frequency energy between 9 kHz and 3,000,000 MHz do not cause interference to radio communications.
• 10 CFR Part 430 and 10 CFR Part 429: These regulations set energy efficiency standards and certification requirements for LED headlights, including parameters such as input power, lumen output, lamp efficiency, correlated color temperature, power factor, time before failure, etc.

In addition, federal regulations have strict provisions for radio frequency energy and energy efficiency standards for all LED headlights. When installing or modifying LED headlights, car owners should ensure that these regulations are met to avoid violating the law.

Arizona

Headlights: Must be on from sunset to sunrise and in snowy or hail-sleeting days.

High beams: Must be dimmed when approaching a traffic lane 500 feet or approaching another vehicle 200 feet.

California

Headlights: Must be on from 30 minutes after sunset to 30 minutes before sunrise, when you cannot see more than 1,000 feet away, and when using windshield wipers. California also recommends that drivers turn on their headlights during the day, but it is not required.

High beams: Must be dimmed when approaching a traffic lane 500 feet away.

Colorado

Headlights: Must be on from sunset to sunrise, when you cannot see more than 1,000 feet away.

High beams: Must be dimmed when approaching a traffic lane 500 feet or approaching another vehicle 200 feet away.

Delaware

Headlights: Must be on from sunset to sunrise, when you cannot see more than 1,000 feet away, and when using windshield wipers.

High beams: Must be dimmed when approaching 500 feet from a major road or 200 feet from another vehicle.

District of Columbia

High beams: Must be on 30 minutes after sunset to 30 minutes before sunrise, or when you cannot see more than 500 feet and when windshield wipers are in use.

High beams: Must be dimmed when approaching 500 feet from a major road or 300 feet from another vehicle.

Florida

High beams: Must be on from sunset to sunrise.

High beams: Must be dimmed when approaching 500 feet from a major road or 300 feet from another vehicle.

Georgia

High beams: Must be on 30 minutes after sunset to 30 minutes before sunrise and when it is raining.

High beams: Must be dimmed when approaching 500 feet from a major road or 200 feet from another vehicle.

Hawaii

Headlights: Must be on 30 minutes after sunset to 30 minutes before sunrise, or when you cannot see more than 500 feet.

High beams: Must be dimmed when approaching a road of traffic.

Idaho

Headlights: Must be on from sunset to sunrise, or when you cannot see more than 500 feet.

High beams: Must be dimmed when you are 500 feet from a road of traffic or 200 feet from another vehicle.

Illinois

Headlights: Must be on from dusk to dawn and when using windshield wipers.

High beams: Must be dimmed when you are 500 feet from a road of traffic or 300 feet from another vehicle.

Iowa

Headlights: Must be on from sunset to sunrise, or when you cannot see more than 500 feet.

High beams: Must be dimmed when you are 1,000 feet from a road of traffic or 400 feet from another vehicle.

Texas

Headlights: Must be on from 30 minutes after sunset to 30 minutes before sunrise or when the visibility is less than 1,000 feet away.

High beams: You may not use headlights when driving in fog, rain or snow. You must dim your high beams when you are 500 feet closer to a traffic lane or 300 feet closer to another vehicle.

Virginia

Headlights: Must be on from sunset to sunrise, in fog, rain or snow, or when the visibility is less than 500 feet away.

High beams: You may not use headlights when driving in a city, unless there are no street lights. You must dim your high beams when you are 500 feet closer to a traffic lane or 200 feet closer to another vehicle.

Washington

Headlights: Must be on from 30 minutes after sunset to 30 minutes before sunrise, when visibility is poor or when the visibility is less than 500 feet away.

High beams: You may not use headlights when driving in fog, rain or snow. High beams must be dimmed when approaching 500 feet from a traffic lane or 300 feet from another vehicle.

Pennsylvania

High beams: must be on from sunset to sunrise, when windshield wipers are in use, or when you cannot see more than 1,000 feet.

High beams: must be dimmed when approaching 500 feet from a traffic lane or 300 feet from another vehicle.

New York

High beams: must be on from 30 minutes after sunset to 30 minutes before sunrise, when windshield wipers are in use, or when you cannot see more than 1,000 feet.

High beams: must be dimmed when approaching 500 feet from a traffic lane or 200 feet from another vehicle.

New Jersey

High beams: must be on from 30 minutes after sunset to 30 minutes before sunrise, in fog, when windshield wipers are in use, or when you cannot see more than 500 feet.

High beams: Must be dimmed when approaching another vehicle.

Massachusetts

High beams: Must be on from 30 minutes after sunset to 30 minutes before sunrise, when windshield wipers are in use, when traveling through a tunnel, or when you cannot see more than 500 feet away.

High beams: Must be dimmed when approaching a lane of traffic within 500 feet or another vehicle within 200 feet.

Michigan

High beams: Must be on from sunset to sunrise, in rain or snow, or when you cannot see more than 500 feet away.

High beams: Must be dimmed when approaching a lane of traffic within 1,000 feet or another vehicle within 200 feet.

Maryland

High beams: Must be on when windshield wipers are in use or when you cannot see more than 1,000 feet away.

High beams: Must be dimmed when approaching a lane of traffic within 500 feet or another vehicle within 300 feet.

Nevada

Headlights: Must be on from 30 minutes after sunset to 30 minutes before sunrise or when you cannot see more than 1,000 feet.

High beams: Must be dimmed when you are within 500 feet of a traffic lane or 300 feet of another vehicle.

Headlight Quality:How to select headlight bulb?

Final thoughts.  Generally, aftermarket LED headlights are illegal for use on the road in the US.  If you choose to install them anyways, they can provide a benefit to the driver of the vehicle in most operating conditions.  Due to the design and poor function of the factory headlights on my daily driver.  I chose to upgrade to LED headlight assemblies, and I now enjoy driving the vehicle more at night.  When I drove other vehicles with halogen lights, I found myself missing the whiter light of the LEDs.  If you decide to install LED headlights, I recommend replacing them as a complete light assembly designed around the LED light source.  This provides a more controlled, useable light pattern down the road.   Manufacturers of high-quality light assemblies are more likely to better adhere to the FMVSS and may offer them with a legitimate DOT test rating.  They are more expensive, but worth it for the quality of the light output and longevity of the bulb.  If you choose to install LED bulbs in your factory halogen headlight assemblies, I recommend getting them aimed.  It can help to reduce the number of times you get flashed from people thinking you have your high beams on.