California window tint law, window by window.

The short version

Most of the questions we get boil down to one number: 70%. That is the minimum visible light transmission (VLT) for the front side windows, measured with the film on the glass. The law also says the film on the fronts must be a near-clear film, meaning 88% VLT or lighter on its own. Everything behind the driver's door is open. The windshield is a strip at the top and nothing else, unless a doctor has signed off.

Front side windows: 70% combined, near-clear film

The front side windows are the driver's and front passenger's door glass. Two conditions apply at once. First, the glass plus the film has to pass at least 70% of visible light. Second, the film itself has to be near-colorless with a VLT of 88% or more. In practice that means a light ceramic film. STEK SMART+ 70 or NEX+ 70 on the fronts stays legal on most factory glass and still rejects around 60% of infrared heat, which is the whole point of ceramic film: heat rejection without darkness.

Factory front glass is usually lightly tinted from the plant, often in the 75% to 80% range. That is why a "70% film" on the fronts can still fail a meter reading. We check the factory glass before we quote fronts, and we will tell you if your car has no room.

Rear side windows and back glass: any shade

Behind the B-pillar, California sets no darkness limit. The only condition is that the vehicle has outside mirrors on both sides, which every modern car does. This is where 20% and 5% films live, and where most of the privacy and heat benefit comes from. On an SUV or truck with factory privacy glass, we usually match the rear film to the factory tone so the car looks consistent from outside.

Windshield: the AS-1 strip, or a medical letter

Look at the top corner of your windshield for a small "AS-1" marking. Film is allowed above that line and nowhere else. On most vehicles that strip is four to five inches deep. A full windshield film in any shade needs a signed medical exemption. One exception added in 2017: a clear, colorless UV film that passes 70% or more visible light and meets the reflectivity rule is allowed on the windshield without a letter. That is a niche product; if you want it, ask and we will source it.

The medical exemption

A licensed physician, surgeon, dermatologist or optometrist can write a letter stating you need protection from the sun for a medical condition. Lupus, certain skin cancers, and light-sensitivity conditions are the common ones. With that letter in the car, you can carry darker film on the front side windows and the windshield. Bring the letter to the appointment. We keep a copy with your job record and install to what the letter supports.

What is never allowed

• Film more reflective than ordinary window glass. Mirror and metallic-look films are out.
• Red, amber or blue tints, on any window.
• Anything that blocks the driver's view through the front windshield below the AS-1 line without an exemption.

None of the three STEK lines we install is reflective or colored, so this only comes up when we remove someone else's old film.

What a tint ticket looks like

Illegal tint is a correctable violation. The usual outcome is a fix-it ticket: remove the film, have the correction verified, pay the dismissal fee. The number people fear, several hundred dollars, tends to come from ignoring the ticket or from a second citation. The cost that stings is the film itself, which comes off and does not go back on. That is the reason we will not install a dark front even when a customer asks. We would rather lose the upsell than have you strip it in a month.

How we install to the law

1. We meter your factory front glass before quoting front windows.
2. Fronts get a 70-series ceramic film only, unless you bring a medical letter.
3. Rear sides and back glass get the shade you pick: 35, 20 or 05 are the common calls.
4. Windshield gets the AS-1 strip by default. Full windshield only with the letter.
5. You leave with a receipt that names the film and shade on each window, which is what an officer or a smog tech will ask about.

Bottom line

Legal tint in California is not restrictive if you understand the split: keep the fronts light and ceramic, go as dark as you want in back, leave the windshield alone below the strip. Done that way, you get most of the heat rejection and all of the privacy without ever thinking about a meter. Film choices, shades and prices are on the window tint page.