Components and options for laying out your Bootstrap project, including wrapping containers, a powerful grid system, a flexible media object, and responsive utility classes.
Containers are the most basic layout element in Bootstrap and are required when using our default grid system. Choose from a responsive, fixed-width container (meaning its
max-width changes at each breakpoint) or fluid-width (meaning it’s
100% wide all the time).
While containers can be nested, most layouts do not require a nested container.
.container-fluid for a full width container, spanning the entire width of the viewport.
Since Bootstrap is developed to be mobile first, we use a handful of media queries to create sensible breakpoints for our layouts and interfaces. These breakpoints are mostly based on minimum viewport widths and allow us to scale up elements as the viewport changes.
Bootstrap primarily uses the following media query ranges—or breakpoints—in our source Sass files for our layout, grid system, and components.
Since we write our source CSS in Sass, all our media queries are available via Sass mixins:
We occasionally use media queries that go in the other direction (the given screen size or smaller):
Note that since browsers do not currently support range context queries, we work around the limitations of
max- prefixes and viewports with fractional widths (which can occur under certain conditions on high-dpi devices, for instance) by using values with higher precision for these comparisons.
Once again, these media queries are also available via Sass mixins:
There are also media queries and mixins for targeting a single segment of screen sizes using the minimum and maximum breakpoint widths.
These media queries are also available via Sass mixins:
Similarly, media queries may span multiple breakpoint widths:
The Sass mixin for targeting the same screen size range would be:
Several Bootstrap components utilize
z-index, the CSS property that helps control layout by providing a third axis to arrange content. We utilize a default z-index scale in Bootstrap that’s been designed to properly layer navigation, tooltips and popovers, modals, and more.
These higher values start at an arbitrary number, high and specific enough to ideally avoid conflicts. We need a standard set of these across our layered components—tooltips, popovers, navbars, dropdowns, modals—so we can be reasonably consistent in the behaviors. There’s no reason we couldn’t have used
We don’t encourage customization of these individual values; should you change one, you likely need to change them all.
To handle overlapping borders within components (e.g., buttons and inputs in input groups), we use low single digit
z-index values of
3 for default, hover, and active states. On hover/focus/active, we bring a particular element to the forefront with a higher
z-index value to show their border over the sibling elements.