How Dark Can Your Window Tint Be in the UK?
The front glass has a hard legal limit; the rear has none. Here is exactly how dark you can go, and where most aftermarket film crosses the line.
Window tint is conditional in the UK. The front windscreen must let at least 75% of light through and the front side windows at least 70%. Behind the driver there is no limit, so rear glass can be as dark as you like.
How dark you can legally go depends entirely on which window you mean. UK law only restricts the glass in front of the driver, and it does so with two fixed numbers.
The two numbers that matter
The whole test comes down to light transmission, the percentage of light that passes through the glass. The front windscreen must let at least 75% through. The front side windows must let at least 70% through. Those two figures apply to every car on UK roads, whatever its shape or age. Film is rated by how much light it blocks, so a film that looks fine on its own can still drop the front glass under the limit once it is added to already-tinted factory glass.
The rear glass has no limit
There is no legal restriction on the rear windscreen or the rear side windows. They can be tinted as dark as you want, including near-black privacy film. Many cars already leave the factory with darker glass behind the driver for exactly this reason. So the popular blacked-out look is perfectly legal at the back; it is only the front that is capped.
Where most aftermarket tint fails
Most film sold as 5%, 20% or 35% puts the front side windows well below the 70% mark, which makes it illegal to use on the road. Police and DVSA examiners measure tint at the roadside with a calibrated light meter, so it is not a judgement call. Go too dark on the front and you can be handed a prohibition notice that takes the car off the road until the film is removed, and fitting or selling over-tinted glass is a separate offence. Full detail: Is window tint legal in the UK?
The conditions that matter
- ✓The rear windscreen and rear side windows have no tint limit.
- !The front windscreen must let at least 75% of light through.
- !The front side windows must let at least 70% of light through.
- ✕Dark "limo" film (5% to 35%) on the front windows is not road-legal.
Legal alternatives
If you want a darker look, tint only the rear glass, which has no legal limit, and keep the front windscreen and front side windows above the 75% and 70% light thresholds.
Sources
General guidance, not legal advice. Road-legality varies by exact vehicle and changes over time; confirm with the manufacturer, your insurer and the latest DVSA/GOV.UK guidance before modifying.