For the 2017 Audi A3, the low-beam headlights use LED bulbs. High-beam fitment depends on the headlight type: halogen systems use H15, HID systems use D3S, and LED systems use LED lighting.
Other exterior lighting also varies with the headlight configuration. Front turn signals use 64132 with halogen headlights and LED with LED headlights. Daytime running lights follow the same pattern, using H15 on halogen-equipped models and LED on LED-equipped models. Parking lights are 2825 or 98 with halogen headlights, while LED-equipped models use LED.
The fog light uses 64136. For rear lighting, halogen-headlight models use 7440R for the brake light, 921 for the tail light, and 5008 for the rear turn signal; LED-equipped models use LED for these functions. Reverse-light fitment requires comparing the original bulb: the options listed are 64132 or LED. Interior locations commonly use 2825 or 98, while the vanity light uses 6418.