Containers are the most basic layout element in Bootstrap and are **required when using our default grid system**. Containers are used to contain, pad, and (sometimes) center the content within them. While containers *can* be nested, most layouts do not require a nested container.
Bootstrap comes with three different containers:
-`.container`, which sets a `max-width` at each responsive breakpoint
-`.container-fluid`, which is `width: 100%` at all breakpoints
-`.container-{breakpoint}`, which is `width: 100%` until the specified breakpoint
The table below illustrates how each container's `max-width` compares to the original `.container` and `.container-fluid` across each breakpoint.
See them in action and compare them in our [Grid example]({{< docsref "/examples/grid#containers" >}}).
Responsive containers allow you to specify a class that is 100% wide until the specified breakpoint is reached, after which we apply `max-width`s for each of the higher breakpoints. For example, `.container-sm` is 100% wide to start until the `sm` breakpoint is reached, where it will scale up with `md`, `lg`, `xl`, and `xxl`.
As shown above, Bootstrap generates a series of predefined container classes to help you build the layouts you desire. You may customize these predefined container classes by modifying the Sass map (found in `_variables.scss`) that powers them:
For more information and examples on how to modify our Sass maps and variables, please refer to [the Sass section of the Grid documentation]({{< docsref "/layout/grid#sass" >}}).