Window tint and UK law: what is actually legal

The rule, in one paragraph

For cars first used on or after 1 April 1985, the windscreen must let at least 75% of visible light through, and the front side windows (the driver and passenger door glass) must let at least 70% through. Those figures apply to the glass and film together, not the film alone. There is no legal limit for the rear side windows, the rear quarter glass or the rear screen. The regulation is the Road Vehicles (Construction and Use) Regulations 1986, regulation 32.

Light transmission is measured as VLT, visible light transmission, as a percentage. A window showing 70% VLT lets 70% of the light through and blocks 30%. Lower numbers are darker.

Why the front limits bite harder than you think

Factory glass is not 100% clear. A typical front door window leaves the factory somewhere between 80% and 90% VLT before any film touches it, and a windscreen is made to meet its 75% minimum with very little headroom above it. Add a film that transmits 70% of light to a window that already transmits 85% and the combined result is roughly 60%, which is illegal. That is why the darkest front-side film we will fit on most cars is a very light shade, and why some cars cannot legally take any film on the fronts at all.

We measure the glass with a VLT meter before recommending a front film, and we measure again after fitting. If the glass and film together fall under the limit, the film comes off. The ranges we fit include shades light enough for legal fronts, which is the only reason we will do front side windows at all.

The windscreen is not a candidate for a shade film in any practical sense. A near-clear heat-rejecting film can sometimes stay inside the 75% limit on a screen with good factory transmission; a visible tint cannot. A sun strip across the top of the screen is tolerated in practice provided it stays clear of the area the wipers sweep, but it is not a separate legal exemption.

What happens if the fronts are too dark

• A police officer can measure the glass at the roadside. Below the limit, expect a prohibition notice that stops the car being driven until the film is removed, and potentially a fixed penalty.
• A car with illegal front tint can fail its MOT. Testers check the windscreen and front side windows.
• An insurer can treat an undeclared and illegal modification as grounds to reduce or refuse a claim.
• Dark fronts are also worse to drive with at night and in rain, which is the reason the limit exists.

None of this applies behind the driver. Rear side windows and the rear screen can be as dark as you like, with the one practical caveat that a rear screen with no rear-view mirror visibility relies entirely on the door mirrors.

Myths we hear every week

• "Factory privacy glass is a tint, so the front rule does not apply." Factory privacy glass is dark glass, not film, and manufacturers only fit it behind the driver for exactly this reason.
• "A light film is fine on the fronts, everyone has it." Only if the measured total stays at or above 70%. Many cars with a light front film measure well under it.
• "The police do not check." Some forces carry meters and do check, especially when the car has been stopped for something else.
• "Removing the film later puts everything right." It does, but the prohibition, the penalty and the failed MOT have already happened.
• "Ceramic film is legal because it is clear." Ceramic describes how the film rejects heat, not how dark it is. Ceramic films come in every shade, including illegal ones.

What we will and will not fit

We fit rear glass to whatever shade you want, from a light privacy tint to the darkest film in the range. We fit front side windows only with a film that keeps the measured total at or above 70%, and we say no to anything darker however nicely we are asked. We do not fit shade films to windscreens. Every car is measured before and after, and the measured figures go on the paperwork with your written quotation and warranty.

If you want to see how a shade looks before deciding, our tint configurator shows each film on a car, window by window, with the legal limit flagged on the front glass. It uses the manufacturers’ published figures for the films we fit.