Navbar
Similar to Nav, Navbar is a base component used to create other horizontal navigation like bars (e.g., Navigation Bar, Management Bar, and Application Bar). Navbar on its own doesn't have any special color styling. Colors can be modified using a combination of Bootstrap 4's Navbar color utilities.navbar-light,.navbar-darkand background utilities. We don't recommend using color utilities as it's hard to keep track of the colors in large applications, rather we recommend scoping your color class to the component and using theclay-navbar-variant($map)mixin to customize colors that are not covered by any of the Navbar variants.
Bootstrap 4 doesn't support Dropdown Menu's with Popper.js positioning inside Navbars. They align them manually via CSS classes. See Dropdown Alignment.
Navbar-breakpoint-down-d-block, Navbar-breakpoint-down-d-inline-block, Navbar-breakpoint-down-d-flex, Navbar-d-breakpoint-down-none
navbar-breakpoint-down-d-noneis a helper class to hide content at it's expand breakpoint e.g. for.navbar-expand-md,navbar-breakpoint-down-d-nonewilldisplay: none;at screen widths less than or equal to 767px.
Navbar Toggler
navbar-toggleris the button that opens and closes the navbar in mobile, must be used with the collapse plugin.