Bootstrap provides several form control styles, layout options, and custom components for creating a wide variety of forms.
## Contents
* Will be replaced with the ToC, excluding the "Contents" header
{:toc}
## Form controls
Bootstrap's form controls expand on [our Rebooted form styles]({{ site.baseurl }}/content/reboot/#forms) with classes. Use these classes to opt into their customized displays for a more consistent rendering across browsers and devices. The example form below demonstrates common HTML form elements that receive updated styles from Bootstrap with additional classes.
Remember, since Bootstrap utilizes the HTML5 doctype, **all inputs must have a `type` attribute**.
<smallid="fileHelp"class="text-muted">This is some placeholder block-level help text for the above input. It's a bit lighter and easily wraps to a new line.</small>
Below is a complete list of the specific form controls supported by Bootstrap and the classes that customize them. Additional documentation is available for each group.
Since Bootstrap applies `display: block` and `width: 100%` to almost all our form controls, forms will by default stack vertically. Additional classes can be used to vary this layout on a per-form basis.
### Form groups
The `.form-group` class is the easiest way to add some structure to forms. Its only purpose is to provide `margin-bottom` around a label and control pairing. As a bonus, since it's a class you can use it with `<fieldset>`s, `<div>`s, or nearly any other element.
Use the `.form-inline` class to to display a series of labels, form controls, and buttons on a single horizontal row. Form controls within inline forms behave differently:
- Controls are `display: inline-block` to provide alignment control via `vertical-align` and `margin`.
- Controls receive `width: auto` to override the Bootstrap default `width: 100%`.
- Controls **only appear inline in viewports that are at least 768px wide** to account for narrow viewports on mobile devices.
Because of this, you may need to manually address the width and alignment of individual form controls. Lastly, as shown below, you should always include a `<label>` with each form control.
For more structured form layouts, you can utilize Bootstrap's predefined grid classes (or mixins). Add the `.row` class to form groups and use the `.col-*` classes to specify the width of your labels and controls. To vertically center the labels with the textual inputs—nearly anything with `.form-control`—use the `.form-control-label` class.
Checkboxes are for selecting one or several options in a list, while radios are for selecting one option from many.
Disabled checkboxes and radios are supported, but to provide a "not-allowed" cursor on hover of the parent `<label>`, you'll need to add the <code>.disabled</code> class to the parent `.radio`, `.radio-inline`, `.checkbox`, or `.checkbox-inline`.
### Default (stacked)
{% example html %}
<divclass="checkbox">
<label>
<inputtype="checkbox"value="">
Option one is this and that—be sure to include why it's great
By default, browsers will treat all native form controls (`<input>`, `<select>` and `<button>` elements) inside a `<fieldset disabled>` as disabled, preventing both keyboard and mouse interactions on them. However, if your form also includes `<a ... class="btn btn-*">` elements, these will only be given a style of `pointer-events: none`. As noted in the section about [disabled state for buttons](../buttons/#disabled-state) (and specifically in the sub-section for anchor elements), this CSS property is not yet standardized and isn't fully supported in Opera 18 and below, or in Internet Explorer 11, and won't prevent keyboard users from being able to focus or activate these links. So to be safe, use custom JavaScript to disable such links.
{% endcallout %}
{% callout danger %}
#### Cross-browser compatibility
While Bootstrap will apply these styles in all browsers, Internet Explorer 11 and below don't fully support the `disabled` attribute on a `<fieldset>`. Use custom JavaScript to disable the fieldset in these browsers.
{% endcallout %}
## Readonly inputs
Add the `readonly` boolean attribute on an input to prevent modification of the input's value. Read-only inputs appear lighter (just like disabled inputs), but retain the standard cursor.
No official help text classes exist in Bootstrap 4 (previously we had `.help-block` in v3), but thanks to our utility classes like `.text-muted`, you can create much more flexible help text as you need it.
Help text should be explicitly associated with the form control it relates to using the `aria-describedby` attribute. This will ensure that assistive technologies – such as screen readers – will announce this help text when the user focuses or enters the control.
Bootstrap includes validation styles for danger, warning, and success states on form controls. To use, add `.has-warning`, `.has-danger`, or `.has-success` to the parent element. Any `.form-control-label`, `.form-control`, and `.text-help` within that element will receive the validation styles.
{% comment %}
{% callout warning %}
#### Conveying validation state to assistive technologies and colorblind users
Using these validation styles to denote the state of a form control only provides a visual, color-based indication, which will not be conveyed to users of assistive technologies - such as screen readers - or to colorblind users.
Ensure that an alternative indication of state is also provided. For instance, you can include a hint about state in the form control's `<label>` text itself (as is the case in the following code example), include a [Glyphicon](../components/#glyphicons) (with appropriate alternative text using the `.sr-only` class - see the [Glyphicon examples](../components/#glyphicons-examples)), or by providing an additional [help text](#forms-help-text) block. Specifically for assistive technologies, invalid form controls can also be assigned an `aria-invalid="true"` attribute.
{% endcallout %}
{% endcomment %}
{% example html %}
<divclass="form-group has-success">
<labelclass="form-control-label"for="inputSuccess1">Input with success</label>
For even more customization and cross browser consistency, use our completely custom form elements to replace the browser defaults. They're built on top of semantic and accessible markup, so they're solid replacements for any default form control.
We hide the default `<input>` with `opacity` and use the `.custom-control-indicator` to build a new custom form indicator in its place. Unfortunately we can't build a custom one from just the `<input>` because CSS's `content` doesn't work on that element.
We use the sibling selector (`~`) for all our `<input>` states—like `:checked`—to properly style our custom form indicator. When combined with the `.custom-control-description` class, we can also style the text for each item based on the `<input>`'s state.
In the checked states, we use **base64 embedded SVG icons** from [Open Iconic](https://useiconic.com/open). This provides us the best control for styling and positioning across browsers and devices.
Custom checkboxes can also utilize the `:indeterminate` pseudo class when manually set via JavaScript (there is no available HTML attribute for specifying it).
<spanclass="custom-control-description">Or toggle this other custom radio</span>
</label>
{% endexample %}
#### Disabled
Custom checkboxes and radios can also be disabled. Add the `disabled` boolean attribute to the `<input>` and the custom indicator and label description will be automatically styled.
Custom selects degrade nicely in IE9, receiving only a handful of overrides to remove the custom `background-image`. **Multiple selects (e.g., `<select multiple>`) are not currently supported.**
The file input is the most gnarly of the bunch and require additional JavaScript if you'd like to hook them up with functional *Choose file...* and selected file name text.
