A cracked windscreen is one of the most common issues UK drivers deal with, especially from stone chips and motorway driving. But when your MOT is coming up, the big question is:
Can a cracked windscreen actually cause a fail?
The answer is: Yes depending on the size and which area the damage is located.
Where the crack is matters!
During an MOT test, the windscreen is checked in different zones, especially the area “A” Zone directly in front of the driver.
Driver’s line of vision (most important area)
If the crack or chip is:
- Larger than 10mm in the driver’s direct view
- Causing distortion or affecting visibility
- This is the “A” zone, The area in the middle of the steering wheel from left to right.
Your car will likely FAIL the MOT immediately
Outside the driver’s view
If the damage is outside the main viewing area:
- Small chips are often allowed
- Slight cracks may pass if they don’t spread
- Outside of what is classed as the “A” zone you are allowed up to 40mm
However, it is still risky because cracks can grow quickly.
Chip vs crack — what’s the difference?
- Chip → Small point of damage, often repairable
- Crack → A line that spreads across the glass, usually worse
A chip can often be repaired cheaply, but once it turns into a crack, replacement is usually needed.
Why a cracked windscreen is dangerous
Even if your car hasn’t failed yet, a cracked windscreen can still be unsafe:
- Weakens the structural strength of the car
- Can spread suddenly with temperature changes
- Can affect airbag performance in serious crashes
- Reduces visibility in sunlight or rain
What you should do if you notice a crack
If you spot a crack:
- Get it checked quickly
- Repair chips before they spread
- Replace the windscreen if the crack is growing
The sooner you fix it, the cheaper it usually is.
Final thoughts
A cracked windscreen might seem like a small issue, but it can easily lead to an MOT failure depending on its size and position.
If you’re unsure, always get it checked before your test — it could save you time, money, and a failed MOT.