this one meta tag will make the page appear correctly on mobile devices. You may need to do other things to get all the other elements to fit.

Here is the one I usually use

<meta name="viewport" content="width=device-width, initial-scale=1">

Here is the one that bootstrap 4 uses, i guess the shrink to fit is useful for something.

<meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">