Will a cracked windscreen fail an MOT?

Wednesday 29th July 2026

Yes, a cracked windscreen can fail your MOT. But it depends on the size of the damage and exactly what part of the glass the crack or chip appears on. A chip as small as 10 mm could fail the test if it falls directly in the driver's line of sight, whereas damage up to 40 mm is allowed almost anywhere else. This guide explains what the MOT tester checks and what most drivers overlook. 

What are the MOT windscreen zones?  

The MOT tester splits the windscreen into two zones and applies different rules to each. 

Zone A is a 290 mm wide strip of glass centred above the steering wheel, covering the driver's direct line of sight through the area your windscreen wipers clean (known as the swept area). Because this is where your vision matters most, the rules here are the strictest. Any chip or crack over 10 mm in diameter here is an automatic MOT fail. 

Zone B covers the rest of the area that your windscreen wipers reach outside Zone A. Damage here is allowed to be larger before it becomes an MOT fail, since it has less impact on your view of the road. Damage is allowed up to 40 mm; anything larger than this fails your MOT. 

Damage outside the swept area near the edges of the glass is assessed differently again and won't usually cause a fail unless it is likely to spread or creates glare that can obstruct your view. Cracks over 50 mm indicate that the whole windscreen needs replacing and can fail if they affect the windscreen's structural integrity. 

Can your windscreen camera fail an MOT? 

Most drivers don't realise that if your car has features such as lane-keep assist, automatic emergency braking or adaptive cruise control, there's a good chance it has a camera mounted behind the windscreen as part of its Advanced Driver Assistance System (ADAS). This camera registers road markings and other vehicles to make those systems work. 

When you replace your windscreen, the camera has to be recalibrated. If it doesn't get recalibrated, the ADAS system can misjudge the lane position, following distance or braking triggers. This calibration is now part of MOT compliance requirements for ADAS-equipped vehicles from 2024 onwards. Even a small misalignment can cause a system fault or an MOT test failure. 

Do windscreen wipers and washers affect the MOT too? 

Yes. The windscreen isn't the only component assessed. Your tester also checks: 

• Your wiper blades for tears, looseness or inability to clear the screen properly. 

• If your windscreen wipers are dirty or badly worn, they can cause deep scratches in the driver's line of vision, and this could also cause your vehicle to fail an MOT. 

• The washer fluid for a working pump, clear jets and enough fluid in the reservoir to clean the screen on demand. 

You should check these areas before your MOT test as most windscreen wiper and washer bottle issues are easy and inexpensive to put right. 

Could tinted windscreens fail an MOT? 

To pass your MOT your windscreen must be above the minimum legal light transmission level; anything fitted that reduces visibility could fail the test. So be careful if you choose to fit aftermarket tinted film. Other obstructions like stickers, sat-nav mounts, dashcams or air fresheners positioned inside Zone A can be enough to obstruct the driver's view, even if the glass itself is in good condition. 

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