HomeBlogBlogLicense Plate Light Bulbs: Wedge vs Festoon (Sizes)

License Plate Light Bulbs: Wedge vs Festoon (Sizes)

What kind of bulbs go in license plate bulbs?

Most license plate lights use small wedge-style bulbs (like 194/168) or festoon bulbs (commonly 31mm, 36mm, 39mm, or 42mm). The exact type depends on your vehicle’s license plate light housing—some take a push-in wedge bulb, while others use a cylindrical festoon that clips between two contacts.

How to tell which bulb your license plate light uses

The quickest way is to remove one of the existing bulbs and match it by shape and size. A wedge bulb has a flat plastic base with two thin contact wires and pushes straight into the socket. A festoon bulb is a tube with metal caps on each end and sits between spring-loaded tabs.

If yours is a festoon style, length matters. Even a few millimeters can keep the bulb from seating correctly or from making solid contact. 36mm festoon bulbs are especially common on many European vehicles, including a wide range of VW applications.

LED vs. halogen for license plate bulbs

Halogen bulbs are the factory choice on many cars, but LED replacements are popular for a whiter color and longer service life. When upgrading to LED, pay attention to two things: fitment (wedge vs. festoon and the correct length) and compatibility with your vehicle’s bulb monitoring system.

Some vehicles—particularly many VW, Audi, BMW, and Mercedes models—can trigger a bulb-out warning or flickering if the LED doesn’t draw the expected load. In that case, a CANbus-compatible LED (or an LED with built-in error cancellation) is typically the cleanest swap.

Choosing the right festoon size (a common pain point)

If your license plate light uses a festoon bulb, measure the overall end-to-end length of the original. Common sizes include 31mm and 36mm; mixing them up is easy because they look similar at a glance. If you’re shopping specifically for a 36mm CANbus-style option and want a vehicle-focused walkthrough, see the detailed guide here: https://ellixuro.com/guide-vw-36mm-canbus-led-festoon-bulbs-license-plate-lights/.

FAQ

Why do LED license plate bulbs flicker or show a bulb-out warning?

Many vehicles monitor exterior bulbs and expect a certain power draw. If the LED draws too little, the car may pulse the circuit or flag an error; a CANbus-compatible LED or proper load solution usually fixes it.