It’s common practice for insurers to offer separate windscreen cover as part of a comprehensive car insurance policy. However, this standard cover will mean you’ll have to pay the full excess even if you only have a tiny chip (excess being the contribution you need to pay towards that claim).
It can be better value to take out windscreen cover as an optional extra, like you would with breakdown cover if it's not included on your main policy. You will simply pay the excess for each claim making it a considerably cheaper option. It should also not affect your no claims bonus (how many years you haven’t made a claim on your car). Whereas if you don’t have the separate cover, you’ll have to pay the full excess and possibly lose your no claims bonus.
Windscreen damage is a regular claim as the tiniest of chips could eventually cause more significant damage. It’s important to not assume windscreen cover is included in your standard policy. It’s worth double-checking your policy and considering purchasing separate windscreen cover if you are buying a new car insurance policy.