How website's layout changes while using computer and mobile?

Question

There are so many websites which's layouts are different while using computer and mobile. facebook.com, aliexpress.com are example. So, do I have to code two different time for two different device? or there is an amother way?

Answer 1

use this meta tag and it should help for responsive web design
<meta name="viewport" content="width=device-width, initial-scale=1.0">

Answer 2

Use <meta> tag for responsive web design.
This helps to change the width of the output screen according to the device used by you
Insert this code:
<meta name = "viewport" content = "width=device-width, initial-scale = 1.0">

Answer 3

And also except meta tag you need to use @media in CSS.