The Brightest 921 led Headlight bulbs in 2023

This is a buying guide for the brightest 921 LED Headlight Bulbs.

For the last 6 months I’ve been testing a variety of the most well known 921 led bulbs to find the brightest and best available. My considerations included price, longevity and a variety of different features. As always this is an unbiased, non affiliated guide on the brightest 921 led bulbs available. 

Before we get started, remember that 921 bulbs are usually used for tail lights and not your front headlights. Although they could technically work as front headlights,. hey wouldn’t be bright enough and you’ll need to check with your car and its fitment.

It’s highly recommended to only use 921 bulbs for your tail lights. If you’re looking for the brightest bulbs for your front headlights then check out some of our other front headlight guides.

IMPORTANT! – Make sure you have the correct bulb sizing and fitment so you don’t waste your money, use this handy tool to double check.

Overall brightest
Marsauto 9006 LED Headlight Bulbs
  • Compatible with vast majority of vehicles
  • Marsauto provide great customer service
  • At least a 50,000 hour lifespan
  • Trusted brand
  • Great customer reviews
  • Extra wide illumination
  • Easy installation
  • No modifications needed
  • 10 year lifespan according to Marsauto
  • 40% higher heat dissipation compared to stock bulbs
  • Reasonable price
  • 20% more illumination range than stock bulbs
  • Built in Y19 CSP 1.9X1.9mm chips
  • 6000K Daylight White
  • 6063 aviation grade aluminum heat sink
  • Minority of customers complain of poor fitting
  • Van owners complain of incompatibility 

Brightest Budget
Car Rover 9006 LED Bulbs
  • Maximum lifespan of 50,000 hours
  • Water resistant
  • Fits in nearly all vehicles
  • Easy installation
  • Similar size to standard halogen bulbs
  • A budget bulb that has a fan
  • Great heat dissipation for price
  • EMC system reduces conflicts with FM radio
  • Antifreeze
  • Cold White 6000K
  • 12000 lumens
  • Adjustable mount 
  • Built in cooling fan
  • Aviation aluminum heatsink
  • 10,000 RPM fan
  • LED
  • Plug and play
  • Built in EMC system
  • Not as bright relative to higher price points
  • Poor instruction manual 
  • Supplied O ring can be too small in some cases
  • Does not fit a 2007 Chevrolet Silverado

Premium Choice
SEALIGHT X2 High Beam Low Beam LED Headlight Bulbs
  • Overwhelmingly positive customer reviews
  • Total reach of 1600 FT
  • 600% brighter than standard halogen bulbs
  • Focused beam doesn’t blind other drivers
  • Manufacture promises a 20 year lifespan if you drive 6 hours a day with the bulbs on
  • Outlasts 180 standard halogens
  • Passed 90F-30 days of high temperature testing
  • Easy fitment and installation
  • Similar sized to standard halogens
  • Upgraded circuit chips prevent ensures no flickering or error warnings
  • Waterproof
  • Kit comes with zip ties and wires
  • 20,000RPM High Speed Silent Fan
  • 600K cool white
  • 16000 lumens
  • 50Watts per bulb
  • 4500LUX per bulb
  • In rare cases some vehicles need anti flicker harness
  • Expensive


Alla Lighting Xtreme Super Bright 921 LED Bulbs

Overall Brightest

A fan to funnel away heat from the bulb is the only heat dissipation technology Alla didn’t include. Since they made their bulbs some of the brightest, I’m not surprised at all the different heat reduction and dissipation features they’ve included. 


A bulbs driver is the part that connects to your car’s wire, a lot of the time this bit is the first thing to break, especially when heat is being poorly funneled. Alla are using separate parts for their IC driver and no polarity driver, this means you can replace them if they fail, but more importantly it reduces the heat on the IC driver. 

They’ve added heat conducting copper pcb around the bulb itself. This piece of copper quickly dissipates heat and moves on to the radiator. This is the most important part in reducing the heat surrounding the bulb. Lastly the housing of this 921 bulb is made of aviation aluminium, it works great at dissipating heat although every bulb uses these days. 


Alla is confident in the longevity of this 921 bulb and they stand by a year warranty, this is a nice thing to have and not to mention the overwhelmingly positive customer reviews to back them up.

  • LED
  • Made of aviation Aluminium
  • 3000 lumens per bulb
  • 360 full angle illumination
  • Plug and play
  • 2 Year warranty
  • CANBUS error free design
  • Trusted brand
  • Easy installation
  • Taillights are significantly brighter
  • Fits all vehicle types
  • Quality heat dissipation
  • Silicon socket rings prevents abrasion or rattling
  • High quality housing body improves overall heat dissipation
  • Heat conducting copper PCB improves heat dissipation 
  • Great customer reviews
  • Vehicles with CAN-BUS systems might require load resistors to avoid error code.
  • No fan 

LASFIT Canbus Ready 921 led bulbs

Brightest Budget

I always like to include a budget choice because there’s a lot of budget options available and a number of these will quickly break on you. I chose Lasfit’s 921 led bulbs because they come with a decent warranty, they’re a trusted brand and I’ve only heard good things from the parts they produce. 



They actually include a Can-Bus system which is surprising for a budget bulb, if you don’t know Can-Bus is an error message that some aftermarket bulbs produce depending on the car, or they might cause strange flickering. Either way, when it happens you’ve got to purchase a separate part known as an extra load resistor to prevent these errors. Lasfit’s new chip prevents the possibility of this happening entirely. 

This definitely is one of the brightest budget 921 led bulbs, it comes with a cool white light and anyone driving from behind won’t miss you. 



What I don’t like is that compared to more expensive options it skimps on reducing heat and funneling it away from the bulb. Its understandable for its price point, though this is a contributing factor for it lasting less time than other bulbs. 

The Bulb

Stock Reverse Light VS LASFIT Canbus Reverse Light

Lasfit’s 921 led bulb does only contain 1500 lumens which is lower than the other 921 led bulbs listed in this guide but still makes it the brightest for its price point. I found it to be far brighter than stock and more than adequate for your tail lights. 

  • Very affordable 
  • 1 Year warranty
  • Specially made to avoid Can-Bus error code
  • Specific fuse prevents chance of high currents causing problems
  • Easy installation
  • Small and easy fit
  • 12 month warranty
  • 45 day money back guarantee 
  • Excellent customer service
  • Great customer reviews
  • LED
  • Plug and Play
  • 1500 Lumens per bulb
  • Worse lifespan compared to more expensive options
  • Lacks a lot of heat dissipation technology 

Diode Dynamics 921 XPR Cool White 921 LED Bulb

Brightest Budget

Diode Dynamics 921 bulb is one of the brightest and also most expensive 921 bulbs on the market. Each bulb contains 16 LEDs, and each LED contains 720 lumens. This makes a total of 11,520 lumens. For tail lights this is maybe as bright as it gets, with this level of brightness you could potentially use these as front headlights.


In the day time your back headlights will still be extremely visible. I’ve attached a photo of what Diode Dynamics 921s look like in the daytime. 


While this was a cloudy day, for back headlights this is as good as you’re going to get. They’re by far the brightest option, bringing  some neat features as well. 

Diode promises a three year warranty and states these bulbs should last years without failure, they use what’s called a constant current circuit which prevents flickering and failure from high voltages or short circuits, and last all of Diode dynamics is manufactured in the USA so you can trust they’re the materials and manufacturing is high quality. 

The Bulbs

In terms of heat dissipation they use a pretty standard aluminium heat sink, while this bulb doesn’t provide all that much bells and whistles in terms of heat dissipation, it’s airflow is designed so that the heat is dissipated away from the 16 LEDs on each bulb. 

  • Manufactured in the USA
  • 3 times more lumens than the competition
  • Excellent brightness
  • 3 year warranty 
  • Extremely visible in the day time
  • Convenient installation
  • Premium and trusted brand
  • Excellent visibility
  • Quality heat sink
  • 16 LEDS
  • 720 Lumens per LED
  • 11,520 lumens in total
  • Plug and Play
  • Aluminium casing
  • Potentially too bright at night
  • Expensive

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Richard Nickleson is the author and owner behind Headlight Reviews. He first started the site as a hobby to share his insights on car parts and specifically headlight bulbs, but it soon ballooned and now he writes on all topics surrounding headlights bulbs. If you've got a bulb question, contact Richard here.

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