css - 请问B站顶部的模糊半透明导航条是怎么实现的呢？

Answer 1

Looking at the code, the frosted glass effect is achieved using filter:blur plus background-image.

For specific methods, please refer to this article

Answer 2

background-color: rgba(255,255,255,0.4);
代码里生效的属性是这么写的。
filter:blur(5px);