Ultimate Audi A4 Bulb Size Chart: Headlights, Tail Lights & Interior Bulbs (All Years)
Last Updated on 2025-11-30
Why bulbs on the Audi A4 matter more than you think
If you drive an Audi A4, your lighting setup quietly controls a huge chunk of your daily driving safety, comfort, and even the way the car feels on the road. People obsess over wheels, suspension, horsepower, all that exciting stuff, and then keep driving around with tired, yellowish bulbs that kill night visibility and make the car look older than it is. Knowing the correct Audi A4 bulb size means you can swap bulbs quickly, avoid buying the wrong parts, and move toward better light output without gambling with random guesses at the parts counter.
I’ve seen plenty of Audi owners turn bulb changes into a mini-drama. Wrong socket, wrong base, broken clip, blown fuse, or that famous “bulb out” warning that pops up and makes you think something expensive broke. When you already know the right Audi A4 bulb size before you start, the whole process gets calmer. You can line up parts, tools, and a game plan and treat it like a predictable task instead of a lottery.
This guide walks through the most common bulb types for all Audi A4 generations from the late 1990s up to the modern models. I’ll cover halogen, xenon/HID setups, typical LED upgrades, and the usual interior bulbs that always seem to fail at the worst moment. Think of this as a practical shortcut: you keep the car roadworthy, you get better light, and you protect your time, energy, and money from silly mistakes.
Quick snapshot of Audi A4 bulb size basics
Before diving generation by generation, it helps to zoom out and see the main patterns. Older Audi A4 models lean heavily on standard halogen bulbs: H7 and H1 for headlights, W5W for side markers and interior, PY21W and P21W for turn and brake lights. As you move into newer generations, xenon/HID options show up (D2S and D3S), followed by trims with full LED setups where the “bulb” is an integrated module rather than a classic replaceable capsule.
When people search for “Audi A4 bulb size” online, they often hope for a single magic table that covers everything. Reality is a bit more nuanced. The platform code (B5, B6, B7, B8, B9), the trim level, and whether the car has halogen, HID, or LED headlights all influence which part number you need. That said, most everyday replacements follow a pattern, and this guide focuses on those common, replaceable bulbs that regular owners actually swap in driveways and garages.
So, if your brain wants the quick cheat sheet: halogens dominate the early years, xenon HIDs become common in mid-life A4s, and LEDs show up strongly in the B8 and B9 series, especially for DRLs and taillights. The rest of the article breaks this down for each generation, so you always know which Audi A4 bulb size applies to your car.
B5 Audi A4 (1996–2001) bulb overview
The B5 Audi A4 kicked off the model line for a lot of markets and brought pretty simple, serviceable lighting. Most cars ran halogen headlights, with xenon options in higher trims, depending on the region. If you have an older A4 and you’re trying to refresh visibility, this is where a clear understanding of Audi A4 bulb size really pays off. You can upgrade to better halogen or LED retrofit bulbs while staying inside the original housings.
| Position | Bulb type & amazon search | Notes |
| Low beam (halogen) | H7 | Main dipped beam on most B5 halogen setups |
| High beam | H1 | Shared reflector with classic bright halogen glare |
| Low beam (xenon option) | D2S | Factory HID projectors on some higher trims |
| Front fog light | H7 | Located in the lower bumper |
| Front turn signal | PY21W | Amber indicator in the headlight housing |
| Front side marker/parking | W5W | Small wedge bulb for position light |
| Tail light (rear position) | P21W | Standard rear running light |
| Brake light | P21W | Shared or separate bulb depending on cluster version |
| Rear turn signal | PY21W | Amber indicator in rear cluster |
| Reverse light | P21W | Single bright white lamp |
| Rear fog light | P21W | Mandatory in many european markets |
| License plate light | W5W | Two small bulbs above the plate |
| Front dome/map light | W5W | Interior overhead console |
| Rear dome light | W5W | Rear passenger area |
| Trunk/cargo light | W5W | Makes loading stuff at night less of a struggle |
When you compare prices, H7 and H1 bulbs are relatively commoditized, so your value comes from picking reliable brands, not random no-name options that fail quickly. The Audi A4 bulb size for this first generation gives you plenty of flex to move into brighter halogen or LED retrofits, as long as you respect heat and beam pattern.
B6 Audi A4 (2002–2005) lighting details
The B6 generation refined the formula. Headlights changed shape, and xenon options became more common. Many owners upgrade these cars because the original halogens fade over time and make the front end feel tired. Knowing the correct Audi A4 bulb size for the B6 lets you plan upgrades without triggering warning errors or melting housings with oversized LEDs.
| Position | Bulb type & amazon search | Notes |
| Low beam (halogen) | H7 | Most common B6 dipped beam |
| High beam | H7 | Often shared reflector design with low beam |
| Low beam (xenon) | D2S | Factory HID with auto-leveling on many cars |
| Front fog light | H11 | Round fogs in the lower grille |
| Front turn signal | PY21W | Amber indicator in headlamp housing |
| Front parking/position | W5W | Small wedge bulb near the projector/reflector |
| Tail light (rear position) | P21W | Standard rear running lights |
| Brake light | P21W | Main stop light in rear cluster |
| High mount stop light | W5W | Third brake light in rear window or spoiler |
| Rear turn signal | PY21W | Amber or clear lens depending on market |
| Reverse light | P21W | White lamp for backing up safely |
| Rear fog light | P21W | Usually one side only |
| License plate lights | W5W | Two small housings at the plate edge |
| Front interior dome/map | W5W | Console above front seats |
| Rear interior lamp | W5W | Roof light for passengers |
| Trunk light | W5W | Single side panel lamp in the cargo area |
The Audi A4 bulb size chart for the B6 looks similar to the B5 at first glance, yet small changes like H11 fogs and more frequent xenon setups create room for smarter upgrades. For example, bright LED reverse bulbs reduce strain when backing into tight parking spots at night, especially if your camera or parking sensors feel a bit dated.
B7 Audi A4 (2005–2008) bulbs and common upgrades
The B7 often feels like a heavy facelift of the B6, and the lighting reflects that. A lot of bulb sizes carry over, which is great for your wallet and your sanity. If you already understand the B6 Audi A4 bulb size scheme, the B7 becomes an easy upgrade playground. Many owners shift to LED parking lights and license plate bulbs for a cleaner, more modern look without touching the headlight internals.
| Position | Bulb type & amazon search | Notes |
| Low beam (halogen) | H7 | Main dipped beam on halogen-equipped cars |
| High beam | H7 | Often shared reflector with low beam |
| Low beam (xenon) | D2S | Xenon projector with clean cutoff |
| Front fog light | H11 | Integrated in the lower grille inserts |
| Front turn signal | PY21W | Amber indicator under the low beam |
| Front parking/DRL (halogen) | W5W | Can be used as position light or DRL in some markets |
| Tail light (rear position) | P21W | Standard rear running bulbs |
| Brake light | P21W | Stop lamps in main cluster |
| High mount stop light | W5W | Third brake light assembly |
| Rear turn signal | PY21W | Amber indicator in rear housing |
| Reverse light | P21W | White reverse lamp |
| Rear fog light | P21W | Usually in the inner cluster section |
| License plate lights | W5W | Two wedge bulbs |
| Interior map/dome | W5W | Front and rear roof lamps |
| Trunk/cargo area | W5W | Side panel light |
If you want a quick cosmetic “bonus” value on a B7, LED license plate bulbs and LED interior bulbs make the cabin feel more modern. Match the Audi A4 bulb size correctly, and you avoid egregious amounts of money wasted on returns, shipping, or trial-and-error purchases that sit in a drawer forever.
B8 Audi A4 (2009–2016) bulb mix: halogen, xenon, and LED
The B8 introduced a more complex mix of technologies. You see halogen base models, xenon projectors with LED daytime running lights, and various tail light configurations. The Audi A4 bulb size situation here gets more differentiated. Some bulbs remain old-school and swappable, while others are integrated into LED strips that require complete lamp replacement if they fail.
| Position | Bulb type & amazon search | Notes |
| Low beam (halogen) | H7 | Standard reflector or projector on base models |
| High beam (halogen) | H7 | Separate high-beam reflector |
| Low beam (xenon) | D3S | Factory HID projector with sharp cutoff |
| Front fog light | H11 | Round fogs low in the bumper |
| Front turn signal (headlight) | PY21W | Halogen indicator separate from LED DRL |
| Front DRL/position (non-led) | W21W | On some markets without LED strips |
| Tail light (rear position, halogen cluster) | P21W | Outer rear lights on basic versions |
| Brake light (halogen cluster) | P21W | Main stop lamps |
| Rear turn signal | PY21W | Amber indicator |
| Reverse light | W16W | Bright white reverse lamp |
| Rear fog light (halogen cluster) | P21W | Single red fog lamp |
| License plate lights | W5W | Can be swapped to LED easily |
| Interior front map/dome | W5W | Some trims use festoon style; check housing |
| Rear interior dome | W5W | Rear passenger lamp |
| Trunk/cargo lamp | W5W | Side-mounted, easy to upgrade to LED |
On B8 cars with LED taillights, many elements are sealed LED modules rather than P21W-style bulbs. That means sometimes your only realistic move is full lamp replacement when a section fails. The rest of the bulbs still follow predictable Audi A4 bulb size patterns and respond well to thoughtful LED upgrades with proper CAN bus compatibility.
B9 Audi A4 (2017–2024) – modern LED-heavy setup
The B9 era brings even more LEDs into the picture. Many trims run full LED headlights, dynamic indicators, and LED tail clusters. You still have some classic bulb sockets around, mainly in fog lamps on certain trims, reverse lights, and parts of the interior. If you drive a B9 and search for “Audi A4 bulb size,” what you really want is a filtered view of which parts are still basic bulbs and which parts live in fancy LED modules that you don’t want to mess with at home.
| Position | Bulb type & amazon search | Notes |
| Low/high beam (full led headlight) | LED module | Integrated factory unit, usually not a DIY bulb swap |
| Low beam (halogen base models) | H7 | Found on some entry-level trims |
| High beam (halogen base models) | H7 | Paired with halogen low beam reflectors |
| Front fog lights (where equipped) | H8 | Lower bumper fog units |
| Front turn signal (halogen setups) | PY21W | Used where dynamic LED indicators are not fitted |
| Tail light (non-full led) | P21W | Some lower trims use halogen tails |
| Brake light (non-full led) | P21W | Main stop lamps on halogen clusters |
| Rear turn signal (non-led indicator) | PY21W | Replaced by dynamic LEDs on higher trims |
| Reverse light | W16W | Great candidate for a quality LED upgrade |
| Rear fog light (non-led) | P21W | In the lower part of the cluster or bumper |
| License plate lights (older b9 years) | W5W | Later cars may use fully sealed LED units |
| Front interior dome/map | W5W | Some trims already use LEDs from factory |
| Rear interior lamp | W5W | Good place to add brighter LEDs without glare |
| Trunk/cargo light | W5W | Helps loads at night feel less like guesswork |
In B9 land, the Audi A4 bulb size situation splits between “old-school bulb sockets you can upgrade freely” and “sealed LED tech where DIY surgery is no bueno.” That split matters for your wallet, your risk tolerance, and your time.
Common lighting problems Audi A4 owners run into
Across all generations, a few problems repeat again and again. Dull low beams, inconsistent color between left and right headlights, random bulb-out warnings, flickering LEDs, and condensation inside the housing. Most of these headaches connect to bulb quality, incorrect Audi A4 bulb size choices, or mismatched technology (throwing in a cheap LED where the car wants a CAN bus-friendly option).
I’ve watched people swap in bright LED reverse bulbs and then wonder why the camera image looks weird, or why the dash complains. The value discrepancy comes from chasing raw lumen numbers while ignoring beam pattern, heat, and electrical load. A balanced approach feels smarter: pick bulbs that fit the correct size, sit properly in the socket, and mimic the load that the car expects.
When condensation appears, people blame the bulb first. Often, the real issue is a damaged housing seal, a missing cap, or a tiny crack in the lens. In that case, you can throw egregious amounts of money at new bulbs and still feel disappointed. Understanding where the weak point sits gives you a cleaner path to real fixes.
How to choose LEDs for your Audi A4 without getting burned
The LED market exploded, which means you have everything from well-engineered options down to absolute niche slap scams. When you pick LED upgrades for any Audi A4 bulb size, you want to think in terms of value, not hype. Brighter bulbs that blind oncoming traffic or cook the inside of the housing are a liability, not an upgrade.
- Match the exact bulb base and size to your original halogen or incandescent bulb before you think about color or brightness.
After that, look for bulbs that mention CAN-BUS compatibility and error-free operation for European cars. That language is sometimes marketing fluff, yet it signals that the manufacturer at least thought about electrical load and not only about raw brightness. Read reviews with a skeptical eye. People who daily drive their cars in winter, rain, and mixed environments give you more realistic feedback than one-time weekend installs.
Color temperature around 4300K–6000K usually gives a good balance between clarity and drama. Go extreme blue, and you slide into cop-magnet territory and poorer performance in rain and fog. Warm white often blends nicely with stock halogens if you’re upgrading one section at a time. When in doubt, pick slightly less wild specs and keep your beam pattern clean. Headlight aim matters more than hype.
Basic replacement tips that make bulb swaps smoother
Every generation has its own quirks, yet a few habits help across the entire Audi A4 lineup. First, look at the backside of the headlight or tail light housing before pulling anything. Many Audi housings hide screws, clips, or sliding tabs. Forcing something usually ends with broken plastic and new profit margins for the parts department.
Second, protect your fingers and the bulb glass. Old-school halogen bulbs hate skin oils. Touch the glass, and you shorten their lifespan. Using gloves or holding bulbs only by the base keeps things clean. LED and HID capsules care more about secure fit and cooling airflow. If the new bulb has a fan or heatsink, tuck wiring carefully so nothing rubs or blocks airflow.
Third, test each bulb right after installation and before fully reassembling trim panels. That single habit wipes out a lot of psychological pain. If you misread the Audi A4 bulb size or got a defective bulb, you catch the error early with easy access, not after you’ve put every screw and plastic clip back in place.
When DIY bulb replacement is unsafe or a bad value
There are moments when do-it-yourself work crosses from “smart frugal move” into “high-risk science project.” On newer cars with full LED headlight modules, complex xenon systems, or tight engine bays, the line gets fuzzy. If your hands barely fit behind the headlight and you’re fighting sharp edges, frustration rises, and the odds of breaking something rise with it.
Airbags, wiring harnesses, and high-voltage HID components can all sit annoyingly close to the things you want to touch. If a manual says to disconnect the battery and remove half the front bumper to reach a particular bulb, that’s the car telling you this is not a casual five-minute job. At that point, trading money for a professional’s time can be a solid guarantee that you won’t turn a simple lighting issue into a larger repair bill.
Another red flag: when warning lights remain on after a bulb swap and you’re tempted to start cutting or bypassing wires. Electrical shortcuts can grate on your belief system later when intermittent faults appear months down the road. When in doubt, step back, reassess, and consider professional help instead of chasing the dopamine hit of finishing the job yourself at any cost.
FAQs about Audi A4 bulb size and upgrades
Q: How do I quickly find my exact Audi A4 bulb size without guessing?
A: Combine this guide with your owner’s manual and the markings on the old bulb. Most bulbs have the type etched or printed on the base. Use that code when ordering replacements instead of relying on vague labels like “headlight bulb.”
Q: Can I put any LED bulb into a halogen socket if the base matches?
A: Physically, maybe. Electrically and optically, not always. You want LED bulbs designed to mimic the filament position of halogens so the beam pattern stays controlled. Otherwise, you risk glare and poor visibility.
Q: Why do some LED bulbs trigger errors on the dashboard?
A: The car expects a certain electrical load from the original bulb. Many LEDs draw less power, so the system thinks the bulb is out. CAN bus-friendly bulbs or load resistors help balance this, although resistors add heat that needs space and ventilation.
Q: Are xenon/HID bulbs worth upgrading on older Audi A4 models?
A: If your current D2S or D3S bulbs look dim or yellow, a fresh pair of quality capsules often feels like a big improvement. Old HIDs fade over time. Matching the correct Audi A4 bulb size and sticking with known-good brands usually pays off.
Q: Do I need to replace bulbs in pairs?
A: For critical lights like low beams, yes, it makes sense. New bulbs are brighter than old ones. Replacing only one can create an odd mismatch that looks cheap and may affect your visibility balance.
Q: Is it safe to open the headlight housing to fix condensation?
A: Light condensation sometimes clears on its own. If water pools inside or the issue keeps returning, check seals and caps first. Fully opening and baking housings is advanced surgery and easy to mess up if you’re not comfortable with that level of work.
Q: Can LED license plate bulbs cause problems with inspections?
A: Usually, inspectors care about brightness, color, and coverage. If the bulbs are bright enough, white, and aimed correctly, they’re fine in most places. Overly blue or flickering bulbs can attract unwanted attention.
Q: How often should I change my headlight bulbs if they still work?
A: Halogens lose intensity over time, even before they burn out. If you drive a lot at night, swapping them every few years keeps your light output closer to original. For HIDs, the decline is slower but still noticeable across many years.
Q: What’s the easiest lighting upgrade for value on an older Audi A4?
A: LED reverse bulbs, LED license plate bulbs, and fresh halogen low beams give a strong dream outcome for minimal effort. You get sharper visibility, a more modern look, and better confidence backing up at night.
Q: Will bulb upgrades affect my car’s resale value?
A: Serious buyers notice clear, bright, consistent lighting. Clean upgrades that match the correct Audi A4 bulb size and keep beam patterns under control can create subtle psychological leverage in your favor during negotiations.
Wrapping up your Audi A4 bulb strategy
Whether you drive a B5 with classic halogens or a B9 packed with LEDs, knowing the right Audi A4 bulb size for each position turns lighting from a vague annoyance into a controllable system. You avoid wasting time at parts counters, you avoid returns, and you dodge pain-inducing experiments with random bulbs that refuse to fit.
Use the tables for your generation, double-check the old bulb markings, and treat LED upgrades as a strategic move rather than an impulse buy. That mindset shifts the lighting game from chaos into clarity. When the sun drops, your A4 still feels ready for anything, and you can say, calmly, “lights are sorted, gimme my money’s worth out of this drive.”
