Vehicle HeadlightPractical lighting guidesCopy the markings exactly, then separate their roles: a source category such as H11, electrical information, manufacturer identification and any product or regulatory markings. No single marking establishes the correct application for your vehicle. Compare the record with the exact manual and official application information, and resolve conflicts before buying.
Read only what is safely available
Start with the retained package, invoice, a clear pre-installation photograph or documentation. Do not remove a hot source, dismantle a lamp or handle energized HID equipment just to read a code. If a character is unclear, write “unreadable” and keep the photograph instead of guessing whether it is a letter or a number.
A brand’s product name may be printed more prominently than the category. For example, “long life” or a color description is not the same kind of information as a source category. OSRAM’s FAQ distinguishes categories such as H1 and H4 from other printed information. [1]
Build a marking record by role
| Information role | How to record it | What it does not establish |
|---|---|---|
| Source category | Copy the complete code, including suffixes. | Every vehicle or lighting function using that category. |
| Electrical marking | Copy voltage and wattage if present; keep units. | Permission to install a higher power source. |
| Manufacturer / product reference | Record brand and full item reference from packaging. | That a similar product name has identical specification. |
| Regulatory or market marking | Copy it and retain its context. | A government-tested approval of your proposed combination. |
| Unknown or unreadable text | Record uncertainty and obtain documentation. | A license to complete the code by appearance. |
Example: the package says H11
An owner sees H11 on a retained halogen package. That is useful category information: SYLVANIA’s catalog includes H11 products. [2] The owner still records the manufacturer’s exact reference, the vehicle’s low-beam entry and the lighting package. A listing that uses H11 in its title is not automatically the same source technology or a verified application.
Write the three records side by side: manual entry, existing-source evidence and official lookup. A mismatch is a reason to ask the manufacturer or repairer which reference applies, not to vote two sources against one. The original part may itself have been wrong.
Treat approval language carefully
The NHTSA interpretation linked here describes a manufacturer self-certification framework and distinguishes integral LED headlamps from replaceable sources. It is dated February 13, 2024. [3] This guide does not turn a printed DOT claim into a current approval of a particular retrofit or decide a state’s installation rules.
Use the compatibility evidence ladder to separate identifying a part from establishing that the complete lamp/source combination is suitable.
Keep the evidence together
- Manual title/edition and the relevant lighting-function section.
- Exact copied marking, with uncertainty preserved.
- Package or invoice reference and date.
- Official lookup result for the exact model, trim, market and function.
- Question to resolve and who supplied the answer.
The local replacement checklist has fields for these items. Its checkboxes record your preparation; they do not certify compatibility. After installation, function and aim remain separate service questions.
Sources and scope
Numbered references support the technical points above. Consulted November 5, 2026. Your vehicle’s documentation takes priority for its specification and service procedure.
- OSRAM: Vehicle lighting FAQ — abbreviations on the bulbPrinted source categories, rated voltage/wattage and manufacturer identification. Markings do not establish the vehicle application.
- SYLVANIA: Replacement headlight bulbs — handling guidanceManufacturer guidance to avoid glass contact and oil transfer. Product catalog is not evidence of vehicle fitment.
- NHTSA: LED headlight interpretation, February 13, 2024Dated federal interpretation distinguishing integral-beam and replaceable-bulb headlamps; state installation rules separate. Not product approval.
Examples and decision tables are editorial illustrations, not diagnoses, product tests or universal instructions. How we work.