California Vehicle Code section 26708 governs how dark your window tint can be. The law is notably asymmetric: the front windows are tightly restricted while the rear glass is almost completely unrestricted. Understanding which windows fall under which rule is the most practical piece of knowledge you need before booking a tint appointment.
Front Side Windows: The 70% Rule
The front driver and front passenger windows must allow at least 70% of visible light to pass through — that is the combined transmittance of the glass and any film applied to it. Factory clear glass typically transmits around 80% of visible light on its own, which means a tinted film on top would push the combined figure below the 70% floor almost immediately.
In practical terms, this means no visibly dark tint is legal on your front windows. A 5% VLT film (limo tint) on the front windows would be illegal. A 20% VLT film would be illegal. Even a 50% VLT film would likely push the combined reading below the 70% threshold once you factor in what the factory glass already absorbs.
The statute (CVC 26708(d)(1)) also sets a separate floor on the film itself: material applied to front side windows must have a minimum visible light transmittance of 88 percent on its own. This is why a shop cannot simply install “70% film” on the front and call the job legal — the film itself must be nearly clear at 88% or better.
What does 70% VLT look like? It is very close to factory clear glass. You will not notice a visible darkening effect on the front windows. What you do gain from a legal ceramic film at 70% VLT is UV protection (99%+ blocked) and meaningful infrared heat rejection — the benefits come from the film's performance characteristics rather than its darkness.
Rear Side Windows: No Darkness Limit
California places no restriction whatsoever on rear side window tint. You can legally apply any VLT — from 70% (nearly clear) all the way down to 5% (limo tint, almost opaque). The choice is entirely aesthetic and practical, not legal.
Most drivers choose 20–35% VLT for rear side windows. At 35% VLT, the tint has a moderate, professional appearance that reduces glare and provides meaningful privacy without feeling cave-like at night. At 20% VLT, the windows are noticeably dark and provide strong privacy for rear passengers and cargo.
Rear Back Window: Also No Limit
The rear back window (rear windshield) follows the same rule as the rear side windows: no darkness limit under California law. Any VLT is legal. The one related requirement is in CVC 26709 — if the rear window is dark enough to substantially obstruct rearward visibility, the vehicle must have side mirrors on both sides. Nearly all modern vehicles already have dual side mirrors, so this is rarely a practical constraint.
Front Windshield: Ceramic Strip Only
The front windshield has its own rule, separate from the side window requirements. California permits a non-reflective strip along the topmost portion of the windshield — commonly described as “above the AS-1 line,” which is a marking etched into the glass by the manufacturer. The statute (CVC 26708(c)(1)) uses a measurement rather than the line itself: the bottom edge of any material must be at least 29 inches above the driver's seat in its rearmost position.
No tinting is permitted below that point on the windshield. Fully transparent UV and infrared films that do not reduce visible light transmittance below factory levels occupy a separate legal category and are worth discussing with an installer if you want windshield protection without a visible strip.
Medical Exemption for Darker Front Windows
California does provide a pathway to darker tint on the front side windows for people with qualifying medical conditions. The exemption under CVC 26708(b)(10) allows front windows down to approximately 35% VLT with a signed statement from a licensed physician or optometrist. The certificate must be kept in the vehicle and presented if questioned.
See our California tint medical exemption guide for the full documentation requirements and what each provision actually permits — the process is more specific than most guides describe.
What “70% VLT” Actually Means
VLT stands for Visible Light Transmission — the percentage of visible light that passes through the window. The number describes transparency, not darkness, which is the opposite of how most people intuitively think about it.
A 70% VLT window allows 70% of visible light to pass through — it is relatively transparent. A 20% VLT window allows only 20% of visible light through — it is much darker. The lower the VLT, the darker the tint. California requiring a minimum of 70% means it is requiring a window that stays close to clear.
| VLT | Appearance | Legal on front windows in CA? |
|---|---|---|
| 70% | Nearly clear, barely visible tint | Yes — minimum legal VLT |
| 50% | Slight, subtle tint visible up close | No — below the 70% threshold |
| 35% | Moderately tinted, common on rear windows | No — illegal on front windows without medical exemption |
| 5% | Very dark, limo tint | No — legal only on rear windows |
What Legal Tint Actually Looks Like in Practice
A common frustration among California drivers is that you cannot tell whether a car has legal front-window tint by looking at it from the outside — compliant 70% VLT film looks almost identical to no film at all. The aesthetic difference between a legal front-window treatment and an untinted car is minimal.
This is why most drivers in California choose to go dark on the rear windows and keep the front nearly clear. A setup with 70% VLT film on the front and 20–35% VLT on the rear creates a gradual transition that looks professional and delivers meaningful heat and UV protection where the rear passengers and cargo need it most.
At Quality Window Tinting we measure VLT after every installation to verify compliance. Our Avery Dennison Encore ceramic films are available in compliant VLT levels for every window position — and even a legal 70% VLT ceramic film provides 99% UV blockage and meaningful heat rejection because those benefits come from the film's infrared performance, not its darkness.