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GoogleThe codes printed in the corner of your windshield, often called the “bug,” identify who made the glass and which safety standard it meets. The word DOT followed by a number is a manufacturer code that the National Highway Traffic Safety Administration assigns to a glass maker that fabricates, laminates or tempers glazing, under the federal glazing standard, FMVSS 205. The AS marking refers to the glazing item in the ANSI/SAE Z26.1 standard that FMVSS 205 adopts, and AS1 is the marking used on windshields. The bug can also show the glass brand, the vehicle maker’s logo and production marks. None of these by itself proves the windshield is the one installed at the factory.
Reading the bug is useful when you buy a used car, check a replacement or want to know what kind of glass you have. This guide is written by Mavi Auto Glass, a locally owned mobile auto glass company based in Roseville that replaces windshields across Sacramento, Rocklin, Folsom, Elk Grove and the rest of Greater Sacramento. It explains each common marking using the federal rule itself, and what the markings can and cannot tell you.
What does the DOT number on a windshield mean?
It identifies the glass manufacturer, not the car. Under 49 CFR 571.205, section S6.2, a manufacturer marks its glazing with the symbol DOT and a manufacturer’s code mark that NHTSA assigns after the manufacturer submits a written request (49 CFR 571.205). The code goes to a prime glazing manufacturer, defined as a company that fabricates, laminates or tempers glazing materials.
Federal Register notices show the code works this way in practice. In one petition, glazing marked DOT287 should have carried the manufacturer’s code DOT540, which shows that the number belongs to a specific maker. The DOT marking is the manufacturer’s own certification that the glass meets the standard, not a separate government test of each windshield.
What do the common windshield markings mean?
Most windshields carry a similar set of marks. The table shows what each one identifies and where the rule comes from.
| Marking | What it identifies | Source |
|---|---|---|
| DOT and a number | The glass manufacturer, through a code NHTSA assigns | FMVSS 205, S6.2 |
| AS1 | The glazing item from ANSI/SAE Z26.1 used for windshields | FMVSS 205, which adopts Z26.1 |
| Laminated | Glass with layers bonded to a plastic interlayer | Printed by the glass maker |
| Glass brand or logo | The company that made or supplied the glass | Printed by the glass maker |
| Vehicle maker’s logo | Glass supplied under the car brand’s name | Printed by the glass maker |
| Other letters, numbers or dots | Production details that vary by manufacturer | Manufacturer’s own system |
FMVSS 205 says glazing materials for motor vehicles must conform to ANSI/SAE Z26.1-1996, and that glazing sold as replacement glass must meet the standard as well. The detailed rules for each AS item are in the Z26.1 standard itself.
Can the markings tell you if the windshield is original?
Not on their own. A DOT number shows who made the glass, and the same glass maker can supply windshields to the automaker and to the replacement market. A vehicle maker’s logo in the bug suggests the glass was supplied under that brand, but the absence of the logo does not prove the glass is poor, and a logo alone does not prove the glass was installed at the factory.
To check a windshield more completely, compare the markings with the other windows of the same car, which usually came from the same supplier, and look for signs of a previous replacement around the edges. Here is a simple way to read it, in 4 steps.
- Find the bug: look in a lower corner of the windshield, usually on the passenger side, from outside the car.
- Read the DOT number and the AS mark: note the code and confirm the AS1 marking.
- Look for logos: check for a glass brand and for the vehicle maker’s logo.
- Compare with the side glass: see whether the door windows carry the same manufacturer and logo.
What should a replacement windshield show in its markings?
It should carry the same kind of safety markings as the original. Under FMVSS 205, glazing intended for replacement must meet the standard, so a replacement windshield should show a DOT manufacturer code and the AS1 marking. Look for these points after a replacement.
- A DOT number and an AS1 marking in the bug
- The word Laminated, or the glass maker’s equivalent marking
- The same features as the old glass, such as the camera bracket, the rain sensor area and the tint band
- An invoice that identifies the glass installed
We use high-quality glass from trusted OEM suppliers, selected for proper fit, optical clarity, durability and safety. Genuine OEM glass is also available upon request and subject to availability. The VIN helps identify the correct windshield for your vehicle, as explained in why auto glass shops ask for your VIN.
Reading your own windshield markings
Take a clear photo of the bug in good light, then note the DOT number, the AS marking and any logos. If you are buying a used car, compare the windshield with the side windows, and if you are getting a windshield replacement, ask which glass is going in and keep the invoice with the photo of the new markings.
