Bootstrap includes a responsive, mobile first fluid grid system that appropriately scales up to 12 columns as the device or viewport size increases. It includes predefined classes for easy layout options, as well as powerful mixins for generating more semantic layouts.
- -Grid systems are used for creating page layouts through a series of rows and columns that house your content. Here's how the Bootstrap grid system works:
-.container (fixed-width) or .container-fluid (full-width) for proper alignment and padding..row and .col-xs-4 are available for quickly making grid layouts. Less mixins can also be used for more semantic layouts.padding. That padding is offset in rows for the first and last column via negative margin on .rows..col-xs-4..col-md- class to an element will not only affect its styling on medium devices but also on large devices if a .col-lg- class is not present.Look to the examples for applying these principles to your code.
- -We use the following media queries in our Less files to create the key breakpoints in our grid system.
-{% highlight scss %} -/* Extra small devices (phones, less than 768px) */ -/* No media query since this is the default in Bootstrap */ - -/* Small devices (tablets, 768px and up) */ -@media (min-width: @screen-sm-min) { ... } - -/* Medium devices (desktops, 992px and up) */ -@media (min-width: @screen-md-min) { ... } - -/* Large devices (large desktops, 1200px and up) */ -@media (min-width: @screen-lg-min) { ... } -{% endhighlight %} -We occasionally expand on these media queries to include a max-width to limit CSS to a narrower set of devices.
See how aspects of the Bootstrap grid system work across multiple devices with a handy table.
-| - | - Extra small devices - Phones (<768px) - | -- Small devices - Tablets (≥768px) - | -- Medium devices - Desktops (≥992px) - | -- Large devices - Desktops (≥1200px) - | -
|---|---|---|---|---|
| Grid behavior | -Horizontal at all times | -Collapsed to start, horizontal above breakpoints | -||
| Container width | -None (auto) | -750px | -970px | -1170px | -
| Class prefix | -.col-xs- |
- .col-sm- |
- .col-md- |
- .col-lg- |
-
| # of columns | -12 | -|||
| Column width | -Auto | -~62px | -~81px | -~97px | -
| Gutter width | -30px (15px on each side of a column) | -|||
| Nestable | -Yes | -|||
| Offsets | -Yes | -|||
| Column ordering | -Yes | -|||
Using a single set of .col-md-* grid classes, you can create a basic grid system that starts out stacked on mobile devices and tablet devices (the extra small to small range) before becoming horizontal on desktop (medium) devices. Place grid columns in any .row.
Turn any fixed-width grid layout into a full-width layout by changing your outermost .container to .container-fluid.
Don't want your columns to simply stack in smaller devices? Use the extra small and medium device grid classes by adding .col-xs-* .col-md-* to your columns. See the example below for a better idea of how it all works.
Build on the previous example by creating even more dynamic and powerful layouts with tablet .col-sm-* classes.
If more than 12 columns are placed within a single row, each group of extra columns will, as one unit, wrap onto a new line.
-With the four tiers of grids available you're bound to run into issues where, at certain breakpoints, your columns don't clear quite right as one is taller than the other. To fix that, use a combination of a .clearfix and our responsive utility classes.
In addition to column clearing at responsive breakpoints, you may need to reset offsets, pushes, or pulls. See this in action in the grid example.
-{% highlight html %} -Move columns to the right using .col-md-offset-* classes. These classes increase the left margin of a column by * columns. For example, .col-md-offset-4 moves .col-md-4 over four columns.
To nest your content with the default grid, add a new .row and set of .col-sm-* columns within an existing .col-sm-* column. Nested rows should include a set of columns that add up to 12 or less (it is not required that you use all 12 available columns).
Easily change the order of our built-in grid columns with .col-md-push-* and .col-md-pull-* modifier classes.
In addition to prebuilt grid classes for fast layouts, Bootstrap includes Less variables and mixins for quickly generating your own simple, semantic layouts.
- -Variables determine the number of columns, the gutter width, and the media query point at which to begin floating columns. We use these to generate the predefined grid classes documented above, as well as for the custom mixins listed below.
-{% highlight scss %} -@grid-columns: 12; -@grid-gutter-width: 1.5rem; -{% endhighlight %} - -Mixins are used in conjunction with the grid variables to generate semantic CSS for individual grid columns.
-{% highlight scss %} -// Creates a wrapper for a series of columns -.make-row(@gutter: @grid-gutter-width) { - margin-left: (@gutter / -2); - margin-right: (@gutter / -2); - &:extend(.clearfix all); -} - -// Make the element grid-ready (applying everything but the width) -.make-col(@gutter: @grid-gutter-width) { - position: relative; - float: left; - min-height: 1px; - padding-left: (@gutter / 2); - padding-right: (@gutter / 2); -} - -// Set a width (to be used in or out of media queries) -.make-col-span(@columns) { - width: percentage((@columns / @grid-columns)); -} - -// Get fancy by offsetting, or changing the sort order -.make-col-offset(@columns) { - margin-left: percentage((@columns / @grid-columns)); -} -.make-col-push(@columns) { - left: percentage((@columns / @grid-columns)); -} -.make-col-pull(@columns) { - right: percentage((@columns / @grid-columns)); -} -{% endhighlight %} - -You can modify the variables to your own custom values, or just use the mixins with their default values. Here's an example of using the default settings to create a two-column layout with a gap between.
-See it in action in this rendered example.
-{% highlight scss %} -.container { - max-width: 60em; - .make-container(); -} -.row { - .make-row(); -} -.content-main { - .make-col(); - - @media (max-width: 32em) { - .make-col-span(6); - } - @media (min-width: 32.1em) { - .make-col-span(8); - } -} -.content-secondary { - .make-col(); - - @media (max-width: 32em) { - .make-col-span(6); - } - @media (min-width: 32.1em) { - .make-col-span(4); - } -} -{% endhighlight %} -{% highlight html %} -max-width to limit CSS to a narrower set of devices.
+
+{% highlight scss %}
+@media (max-width: @screen-xs-max) { ... }
+@media (min-width: @screen-sm-min) and (max-width: @screen-sm-max) { ... }
+@media (min-width: @screen-md-min) and (max-width: @screen-md-max) { ... }
+@media (min-width: @screen-lg-min) { ... }
+{% endhighlight %}
+
+
+
+
+
+### Grid options
+
+See how aspects of the Bootstrap grid system work across multiple devices with a handy table.
+
+| + | + Extra small devices + Phones (<768px) + | ++ Small devices + Tablets (≥768px) + | ++ Medium devices + Desktops (≥992px) + | ++ Large devices + Desktops (≥1200px) + | +
|---|---|---|---|---|
| Grid behavior | +Horizontal at all times | +Collapsed to start, horizontal above breakpoints | +||
| Container width | +None (auto) | +750px | +970px | +1170px | +
| Class prefix | +.col-xs- |
+ .col-sm- |
+ .col-md- |
+ .col-lg- |
+
| # of columns | +12 | +|||
| Column width | +Auto | +~62px | +~81px | +~97px | +
| Gutter width | +30px (15px on each side of a column) | +|||
| Nestable | +Yes | +|||
| Offsets | +Yes | +|||
| Column ordering | +Yes | +|||