Why is the width of the modal window different in different browsers on different devices?

Question

css

I have a Yandex browser and in it the modal window is displayed as it should, but the customer (if I'm not mistaken is a safari) and as far as I know he is a Webkit browser and for some reason the same modal window is wider. What's the matter? in vendor prefixes?

Answer 1

It's more about the system itself. Or in form factor.