For faster mobile-friendly and responsive development, Bootstrap includes dozens of utility classes for showing, hiding, aligning, and spacing content.

Changing display

Use our display utilities for responsively toggling common values of the display property. Mix it with our grid system, content, or components to show or hide them across specific viewports.

Flexbox options

Bootstrap 4 is built with flexbox, but not every element’s display has been changed to display: flex as this would add many unnecessary overrides and unexpectedly change key browser behaviors. Most of our components are built with flexbox enabled.

Should you need to add display: flex to an element, do so with .d-flex or one of the responsive variants (e.g., .d-sm-flex). You’ll need this class or display value to allow the use of our extra flexbox utilities for sizing, alignment, spacing, and more.

Margin and padding

Use the margin and padding spacing utilities to control how elements and components are spaced and sized. Bootstrap 4 includes a five-level scale for spacing utilities, based on a 1rem value default $spacer variable. Choose values for all viewports (e.g., .mr-3 for margin-right: 1rem), or pick responsive variants to target specific viewports (e.g., .mr-md-3 for margin-right: 1rem starting at the md breakpoint).

Toggle visibility

When toggling display isn’t needed, you can toggle the visibility of an element with our visibility utilities. Invisible elements will still affect the layout of the page, but are visually hidden from visitors.