Use any of the available button classes to quickly create a styled button.
Using color to add meaning to a button only provides a visual indication, which will not be conveyed to users of assistive technologies – such as screen readers. Ensure that information denoted by the color is either obvious from the content itself (the visible text of the button), or is included through alternative means, such as additional text hidden with the .sr-only class.
Fancy larger or smaller buttons? Add .btn-lg, .btn-sm, or .btn-xs for additional sizes.
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Create block level buttons—those that span the full width of a parent— by adding .btn-block.
Buttons will appear pressed (with a darker background, darker border, and inset shadow) when active. For <button> elements, this is done via :active. For <a> elements, it's done with .active. However, you may use .active on <button>s (and include the aria-pressed="true" attribute) should you need to replicate the active state programmatically.
No need to add :active as it's a pseudo-class, but if you need to force the same appearance, go ahead and add .active.
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Add the .active class to <a> buttons.
Make buttons look unclickable by fading them back with opacity.
Add the disabled attribute to <button> buttons.
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If you add the disabled attribute to a <button>, Internet Explorer 9 and below will render text gray with a nasty text-shadow that we cannot fix.
Add the .disabled class to <a> buttons.
We use .disabled as a utility class here, similar to the common .active class, so no prefix is required.
This class uses pointer-events: none to try to disable the link functionality of <a>s, but that CSS property is not yet standardized and isn't fully supported in Opera 18 and below, or in Internet Explorer 11. In addition, even in browsers that do support pointer-events: none, keyboard navigation remains unaffected, meaning that sighted keyboard users and users of assistive technologies will still be able to activate these links. So to be safe, use custom JavaScript to disable such links.
While button classes can be used on <a> and <button> elements, only <button> elements are supported within our nav and navbar components.
Use the button classes on an <a>, <button>, or <input> element.
If the <a> elements are used to act as buttons – triggering in-page functionality, rather than navigating to another document or section within the current page – they should also be given an appropriate role="button".
As a best practice, we highly recommend using the <button> element whenever possible to ensure matching cross-browser rendering.
Among other things, there's a bug in Firefox <30 that prevents us from setting the line-height of <input>-based buttons, causing them to not exactly match the height of other buttons on Firefox.