Massachusetts window tint law, in plain words
How dark you can go, how the inspection measures it, and what to do if you need darker glass for a medical reason.
The short answer
At least 35% of the light has to get through the front side windows, the rear side windows and the back window, and the inspector measures the glass and the film together. The windshield can only take a strip along the top 6 inches. Reflective film can reflect no more than 35% of the light.
| Glass | Rule |
|---|---|
| Front side windows | At least 35% of light through |
| Rear side windows | At least 35% of light through |
| Back window | At least 35%, and only with two outside mirrors |
| Windshield | Top 6 inches only (down to the AS-1 line) |
| Reflectivity | No more than 35% |
See the shades on a car
Pick a shade. The lower the number, the darker the glass and the less you see inside.
Why a “35%” film can fail
The inspector's meter reads the glass and the film together. Factory glass already blocks some light, so a film sold as 35% usually measures below 35% once it is on the car, and the car fails inspection. XPEL's own data shows its 35 shades between 34% and 38% on clear glass, before the factory glass is counted. To stay legal, most cars need a lighter film than the number suggests; we measure and help you choose.
Who the 35% rule does not apply to
- Factory tinted glass that meets federal standards (the “privacy glass” many SUVs and trucks come with).
- Cars registered in another state or country.
- Livery vehicles (not taxis), behind the driver.
- Drivers with a tinted glass waiver from the RMV.
Medical exemption (tinted glass waiver)
If a Massachusetts licensed doctor certifies that you are photophobic or photosensitive, the RMV can issue a waiver that allows darker film on the side and back windows (never below the AS-1 line on the windshield). The application is mailed to RMV Medical Affairs, PO Box 55889, Boston, MA 02205 (originals only), and the waiver stays valid for the life of the registration.
If the tint is too dark
The car fails the annual safety inspection. A ticket can cost up to $250, and a third conviction can suspend the driver's license for up to 90 days.
Questions we get
Is 35% tint legal in Massachusetts?
The law requires at least 35% of the light to get through, measured with the glass and film together. A film sold as 35% usually reads lower once it is on factory glass, so many cars need a lighter film to pass inspection.
Can I tint my windshield in Massachusetts?
Only a strip along the top 6 inches, down to the AS-1 line marked on the glass.
Can I tint my back window?
Yes, if the car has two outside mirrors, one on each side, and the same 35% rule applies.
How do I get a medical exemption for darker tint?
A Massachusetts licensed doctor certifies the condition on the RMV's Application for Tinted Glass Waiver, and you mail the original to RMV Medical Affairs, PO Box 55889, Boston, MA 02205.
What happens if my tint is too dark?
The car fails inspection, a ticket can be up to $250, and a third conviction can suspend the license for up to 90 days.
Sources
- Massachusetts General Laws, Chapter 90, Section 9D
- 540 CMR 4.00, annual safety inspection (RMV)
- Massachusetts Vehicle Check: aftermarket window tint guidelines
- Mass.gov: apply for a tinted glass waiver
A plain summary of the law, read on October 1, 2026. It is not legal advice.
Not sure what your car needs?
Text a photo to (857) 888-0120. We tell you what we would do and what it costs.