Smart Fortwo License Plate Bulb Size

The Smart Fortwo license plate light uses bulb size 12961 or DE3423 depending on the specific version of the vehicle. Data for the bulb sizes covers the range from 2008 to 2018.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Bulb Size by Year Range

Years	Bulb Size
2016-2018	12961
2008-2015	DE3423

Bulb Specifications

Description	Bulb Size
Philips part number. Miniature wedge bulb (T10) with W2.1x9.5d base. 12V, 5W.	12961
ANSI standard (US & Canada). Festoon bulb, 41mm length, end-cap contacts. 12V.	DE3423

Other Locations

Additional Notes

The Smart Fortwo uses two distinct bulb types for the license plate position across its model years: the 12961 (a T10 wedge bulb) for 2016-2018 and the DE3423 (a festoon bulb) for 2008-2015.
The 12961 is a Philips part number designation for a T10 miniature wedge bulb. It operates on 12 volts and draws 5 watts, with a W2.1x9.5d wedge base that requires no socket locking mechanism, as the base itself provides retention through friction.
The DE3423 is an ANSI standard designation recognized across the United States and Canada. It is a festoon-style bulb measuring 41mm in length, with flat end-cap contacts on each end that make contact with spring-loaded holders inside the housing.
The wedge base of the 12961 and the end-cap contact design of the DE3423 are physically incompatible with each other. These two bulb types are not interchangeable, as each requires a different socket type within the license plate lamp housing.
Both bulb types operate on a 12-volt electrical system, which is standard for passenger vehicles. However, the DE3423 specification does not include a wattage rating in the provided data, while the 12961 is rated at 5 watts.
The Smart Fortwo (2016-2018) transitioned to the T10 wedge format, which is one of the most widely used bulb form factors in automotive lighting and is commonly available as a direct-fit LED upgrade due to its standardized wedge base.
The festoon format of the DE3423 is held in place by spring tension from the lamp housing rather than a twist or push-lock mechanism, making correct bulb length critical for proper fitment. A bulb that is too short or too long will not make reliable electrical contact.