Popover
A non-modal overlay, showing contextually relevant content and/or actions.
Introduction
NOTE: This pattern was previously known as "flyout".
Popover is a composite pattern containing an element (typically a button) that hosts a non-modal overlay element. The overlay discloses contextually relevant secondary content and/or actions.
Popover forms the basis of the following composite patterns:
The pattern discussed here in this document is a more generic use-case, where the popover may contain any kind of content.
Working Examples
You can take a look at a generic popover on our examples site.
Terminology
popover: the composite pattern as a *whole*, containing an overlay and its host
host: the element that hosts the overlay
overlay: the non-modal overlay that contains the content related to its host
content: the actual content of the overlay
expanded/collapsed: the overlay state (visible or hidden)
Best Practices
The overlay can hold any kind of content, but for an overlay that demands user acknowledgement or input, or with additional rich interactions, consider using a dialog instead.
The overlay expands or collapses via any combination of the following events:
Click event of host
Hover event of host (discouraged)
Focus event of host (discouraged)
System event at page load or after some arbitrary time
A link must not be the host of a click-activated popover. Clicking the host should always navigate to the URL in this case.
Overlay must be non-modal (i.e. must not trap keyboard focus or mask page background). For modal behaviour please consider the dialog pattern instead.
Overlay must be placed directly after the host in DOM. This ensures natural tab order and reading order without JavaScript.
If system-activated (e.g. a Tourtip), overlay must remain onscreen until explicitly dismissed by the user.
If focus-activated, overlay should not contain long blocks of interactive elements. This measure prevents keyboard users from having to tab through secondary or tertiary content inside of the overlay.
Interaction Design
This section provides interaction guidelines for keyboard, screen reader, and pointing devices.
Keyboard
Tab order must flow directly from host into first focusable element inside overlay. If the overlay has no focusable element, tab order flows to next page control instead.
If not system-activated, host must be keyboard focus-able.
If click-activated, popover must expand overlay when host receives keyboard click.
If focus-activated (discouraged), popover must expand when host receives keyboard focus.
If focus-activated (discouraged), popover must collapse when flyout loses keyboard focus.
Screen Reader
Reading order must flow directly from host into overlay.
Overlay must not be conveyed as a dialog.
If system-activated and high-priority, screen reader must announce presence and/or content overlay.
Mouse
If hover-activated (discouraged), popover must expand when host receives mouse hover.
If hover-activated (discouraged), popover must collapse when mouse leaves flyout.
If click-activated, popover must expand when host receives mouse click.
If system-activated, popover must collapse when clicking close button.
Touch
Hover behaviour can be problematic or impossible for touch. You may wish to consider using the Infotip pattern instead.
If click-activated, popover must expand when host receives tap.
if system-activated, popover must close when tapping close button.
Developer Guide
Let's examine a click-activated popovers. Click-activated popovers typically occur with buttons, where clicking the button expands the popover.
The key things to consider are:
Server-side rendering or client-side rendering of overlay content (or both)
Placement of overlay element in relation to host
Using aria-expanded state to toggle CSS display
Determining the live-region property
Content
Content rendered by the server will be visible by default before & without CSS or JavaScript. If the content is secondary in nature, you may wish to render the content on the client instead.
Whatever progressive enhancement strategy you choose, the following structure is the goal:
<span class="popover popover--click">
<button class="popover__host" type="button" disabled>Toggle Popover</button>
<span aria-live="off">
<div class="popover__overlay">
<!-- popover content -->
</div>
</span>
</span>Notice placement of the host (the button) directly before the overlay element. This allows natural keyboard and reading order from the host into the overlay.
An optional live-region element wraps the overlay. The live-region property may be set to "off", "polite" or "assertive".
Presentation
The overlay can be absolute or fixed positioned:
.popover__overlay {
display: none;
position: absolute;
z-index: 1;
}We have hidden the overlay by default (display: none). We use the aria-expanded state of the host to control the display of the overlay:
.popover__host[aria-expanded=true] ~ [aria-live] .popover__overlay {
display: block;
}Behaviour
CSS alone cannot trigger the expanded state, so we require a small amount of Javascript to handle this behaviour:
document.querySelector('.popover__host').addEventListener('click', function() {
const isExpanded = this.getAttribute('aria-expanded') === 'true';
this.setAttribute('aria-expanded', isExpanded ? 'false' : 'true');
});Clicking the button with mouse, keyboard or touch will now toggle the aria-expanded state of the button.
ARIA Reference
aria-expanded
This boolean attribute signifies the expanded state of the host element.
aria-live
If wishing to announce the content of the popover when it expands, set aria live to polite or assertive.
FAQ
Didn't this pattern used to be called Flyout?
Yes it did! In most practical senses, the term flyout is synonomous with popover; they are both used to describe transient (i.e. non-modal) overlays of content.
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