Are you planning to upgrade your car’s headlights? The first step is knowing what socket type your car uses, since each bulb is designed for a specific fit and purpose. (For example, an H1 bulb is a single-beam design used in high or low beam headlights.) If you pick the wrong type, the bulb will sit crooked or even fail to lock into the housing altogether.

Automotive bulbs (regulated under UN Regulation 37) are divided into three groups.

• Group 1 bulbs are approved for all vehicle lighting functions, including headlights and taillights.
• Group 2 bulbs cover the lights for signalling functions such as indicators and brake lights, while,
• Group 3 applies to smaller applications.

In this guide, we’re covering the socket types that are part of Group 1, from the H1 to the H11 bulb.

Identifying the bulb sockets

Headlight bulbs come in different socket types, and sockets are usually grouped by their base design and the number of locking tabs — which is why you’ll often see them listed as part of the H-series or D-series.

Even though LED headlights are becoming more popular, most cars still roll off the factory line with halogen bulbs. And within these, a few socket types dominate — in fact, H7 bulbs, H11 bulbs, and H1 bulbs together fit more than 98% of vehicles on the road. Less common types like the H3 socket are used in narrower applications such as fog lamps.

Let’s take a closer look at the main types:

H1 bulbs

With a single power plug, the H1 bulb is often used in high beams for both 12V and 24V vehicles. Some vehicles also use H1 bulbs in their low beam setup, making them versatile and widely compatible.

H7 bulbs

The H7 bulb has a two-pronged plug and a single-beam design, meaning one bulb is required for high beam and another for low beam. This type is frequently used as the low beam bulb in German and Korean vehicles, as well as Chinese and European cars.

While H4 and H7 bulbs may look similar, they differ in important ways, including base structure and lighting performance. So, it’s best to check for compatibility before replacing them.

H11 bulbs

The H11 bulb is a single-filament halogen bulb with an L-shaped base, making it common for low beams. Some vehicle manufacturers, such as Volkswagen and Kia, also use them for fog lights and daytime running lights.

Drivers sometimes assume that the H8 bulb is interchangeable with H9 and H11 bulbs because they have a similar shape. However, there are differences in their wattage and brightness, as well as application. An H11 bulb may work in a fog light application, but an H9 or H8 bulb may be better suited for specific brightness or power requirements.

H3 bulbs

Although it’s now less common, H3 bulbs are still found in some headlight systems and fog lamps. They require a dedicated socket that provides a secure connection to the electrical circuit. H3 sockets can handle vibrations and moisture well because of their durable, corrosion-resistant materials.

H8 bulbs

Many fog lights use the H8 bulb. Standard halogen versions typically have a service life of around 320 hours and consume about 35 watts of power. They’re not as common as H7 bulbs or the H11 bulb, but they support specific vehicle models that need dedicated fog lights.

Use our Find My Bulb tool

Here at HIDS-Direct, we make it easy and quick to locate the headlights you need. Just enter key details about your vehicle in our Find My Bulb tool, such as its make and model, and you’ll see a list of compatible bulbs and their details. This way, you can shop confidently without second-guessing.

Ready to buy new headlights?

Get access to premium-quality bulbs from trusted brands like Osram and Maruta here at HIDS-Direct. Worried about getting the wrong socket type? We got you with our 30-day no-hassle return policy for your peace of mind.  Shop for H1, H3, H7, H8, and H11 LED bulbs at HIDS-DIRECT to upgrade your vehicle lighting with confidence.