Why do some websites, when scrolling up on ios safari, the address bar at the top get smaller

Question

Why on some websites, when scrolling up on iOS Safari, the address bar at the top becomes smaller

Answer 1

Isn’t it some websites? This is the default behavior of Safari 自带的功能 所有网站都一样
除非禁用原生滚动条和阻止 touchmove events

Answer 2

Already found:
Safari comes with built-in effects. I didn’t trigger this effect at first because it was a page layout error.

Answer 3

for example What about for example?