ARIA: slider role

The slider role defines an input where the user selects a value from within a given range.

Description

The slider role is for range input widgets where the user selects a value from within given minimum and maximum values.

The slider role compared other range options

ARIA provides developers with six different range widget roles, including progressbars, meters, and sliders.

The progressbar role, similar to HTML's <progress> element, is a read-only range indicating the portion of completion of a task, progressing in a single direction, such as a file upload's loading progress bar that eventually reaches 100% when fully loaded.

The meter role, similar to HTML's <meter> element, is a read-only gauge indicating the amount of something within a known range, such as a computer's battery indicator or a car's gas gauge.

The slider role, similar to HTML's input of type range, <input type="range">, is a read-write input range. Sliders allow users to select a value between set minimum and maximum values. The user selects a value by moving a slider thumb along a horizontal or vertical slider to select a value.

While all three of these ranges have the same ARIA states and properties, the slider role is the only read-write range: it is the only one whose value changes via user interaction. As such, it must be able to receive focus. In addition, keyboard interaction, mouse clicks, and touch interaction must be supported.

Warning To change the slider value, touch-based assistive technologies need to respond to user gestures for increasing and decreasing the value by synthesizing key events. Fully test slider widgets using assistive technologies on devices where touch is a primary input mechanism before using the slider role (and all range widgets).

Common attributes

The aria-valuemin attribute sets the minimum value. If omitted or not a number, it defaults to 0 (zero).

The aria-valuemax attribute defines the maximum value. If it is missing or not a number, it defaults to 100.

The aria-valuenow attribute value must be between the minimum and maximum values, inclusive. This attribute is required for slider and meter, and optional for progressbar.

For slider, unless using the <input type="range"> element, the aria-valuenow value must be updated programmatically when the user updates the value.

The optional aria-valuetext attribute is included when the aria-valuenow numeric value doesn't reflect the intended value of the slider. As the minimum, maximum, and current values are all numeric, when the values those numbers represent are not numeric, the aria-valuetext attribute should be included with a string value defining the numeric value. For example, if using a slider for t-shirt sizes, the aria-valuetext attribute should shift from xx-small thru to XX-large as the aria-valuenow increases.

The aria-valuetext value must be updated as the value or aria-valuenow is updated. While there is no equivalent HTML attribute for <input type="range">, you can include aria-valuetext on any <input> type. ARIA attributes are supported on semantic HTML elements.

When aria-valuetext is an important feature for a slider, consider using <select> with <option> elements instead. While not visually a range, every option's value is more accessible to all users, not just users of assistive technology.

An accessible name is required. If the range's role is applied to an HTML <input> element (or <meter> or <progress> element), the accessible name can come from the associated <label>. Otherwise use aria-labelledby if a visible label is present or aria-label if a visible label is not present.

When not using the HTML <input> element to create your slider, include the tabindex attribute to make the slider focusable. Of the three range types, only slider is user-interactive, and so is the only one that requires being able to receive focus. Focus should be placed on the slider thumb.

Sliders have an implicit aria-orientation value of horizontal. This attribute is not supported with meter or progressbar.

User interactions

Unlike the read-only meter and progressbar roles, a slider is an input, accepting user interaction. In addition to including the tabindex attribute to enable slider focus, keyboard and pointer device support must be implemented.

The slider represents the range of possible values. The position of the slider thumb along the slider represents the current value. User actions that must be supported include changing the value by dragging the thumb or clicking the slider for pointing devices and using directional keys such as arrow keys for the keyboard users. See keyboard interactions below.

Note: It is recommended to use native <input type="range"> elements rather than the slider role. User agents provide a stylized widget for the range input element, based on the current value as it relates to the minimum and maximum values. When using non-semantic elements, all features of the native semantic element need to be recreated with ARIA attributes, JavaScript and CSS.

Range with multiple thumbs

A multi-thumb slider is a slider with two or more thumbs that each set a value in a group of related values. For example, in a product search, a two-thumb slider could be used to enable users to set the minimum and maximum price limits for the search.

In many two-thumb sliders, the thumbs are not allowed to pass one another, such as when the slider sets the minimum and maximum values for a range. For example, in a price-range selector, the maximum value of the thumb that sets the lower end of the range is limited by the current value of the thumb that sets the upper end of the range. The minimum value of the upper-end thumb is also limited by the current value of the lower-end thumb.

It is not a requirement that the thumbs in multi-thumb sliders be dependent on the other thumb values, but intuitive user experience is a requirement, so it is recommended to avoid this anti-pattern.

All descendants are presentational

There are some types of user interface components that, when represented in a platform accessibility API, can only contain text. Accessibility APIs do not have a way of representing semantic elements contained in a slider. To deal with this limitation, browsers, automatically apply role presentation to all descendant elements of any slider element as it is a role that does not support semantic children.

For example, consider the following slider element, which contains a heading.

<div role="slider"><h3>Temperature in Celsius</h3></div>

Because descendants of slider are presentational, the following code is equivalent:

<div role="slider"><h3 role="presentation">Temperature in Celsius</h3></div>

From the assistive technology user's perspective, the heading does not exist since the previous code snippets are equivalent to the following in the accessibility tree:

<div role="slider">Temperature in Celsius</div>

Associated roles, states, and properties

aria-valuenow (required)

Set to a decimal value between aria-valuemin and aria-valuemax, indicating the current value of the slider.

aria-valuetext

Assistive technologies often present the value of aria-valuenow as a number. If this would not be accurate, use aria-valuetext to provide the slider with a more understandable value.

aria-valuemin

Set to a decimal value representing the minimum value, and less than aria-valuemax. If not present, the default value is 0.

aria-valuemax

Set to a decimal value representing the maximum value, and greater than aria-valuemin. If not present, the default value is 100.

aria-label or aria-labelledby

Defines the string value or identifies the element (or elements) that label the slider element providing an accessible name. An accessible name is required.

aria-orientation

Indicates whether the element's orientation is horizontal, vertical, or unknown/ambiguous. With a slider, the implicit value is horizontal but can be set to vertical. As it has an implicit value, the slider orientation is never ambiguous.

Examples

In the example below, we create a vertical thermometer with which the user can set the room temperature:

<div>
  <div id="temperatureLabel">
    Temperature
  </div>
  <div id="temperatureValue">20°C</div>
  <div id="temperatureSlider">
    <div id="temperatureSliderThumb"
       role="slider" aria-labelledby="temperatureLabel"
       aria-orientation="vertical"
       tabindex="0"
       aria-valuemin="15.0" aria-valuemax="25.0"
       aria-valuenow="20.0" aria-valuetext="20 degrees Celsius"
       style="top: calc((25 - 20)*2rem - 0.5rem)">
    </div>
  </div>
</div>

The position of the thumb is the maximum value minus the current value times the height of one degree, minus half the height of the thumb to center it. The rest of the styles are static.

[id="temperatureSlider"] {
  position: relative;
  height: 20rem;
  width: 1rem;
  outline: 1px solid;
  margin: 3rem;
}

[id="temperatureSliderThumb"] {
  position: absolute;
  height: 1rem;
  width: 2rem;
  background-color: currentcolor;
  left: -0.5rem;
}

For this example to work, we have to write a script to handle all keyboard and pointer events, including event listeners for pointermove, pointerup, focus, blur, and keydown, and provide styles for the default state and when the thumb and slider receive focus. The position of the thumb, the aria-valuenow andaria-valuetext values, and the inner text of the element with the id "temperatureValue" need to be updated every time ArrowLeft, ArrowDown, ArrowRight, ArrowUp, Home, End, and, optionally, PageDown and PageUp keys are released and when the user drags the thumb or otherwise clicks on the temperature slider.

Using semantic HTML, this could have been written as:

<label for="temperature">
    Temperature
</label>
<output id="temperatureValue">20°C</output>
<input type="range" id="temperatureSlider"
  min="15" max="25" step="0.1"
  value="20" aria-valuetext="20 degrees celsius"
  style="transform: rotate(-90deg);" />

By using <input>, we get an already-styled range-input widget with keyboard focus, focus styling, keyboard interactions, and value updated on user interaction for free. We still need to use JavaScript to change the aria-valuetext and the value of the <output> element.

There are a few ways to make a range input vertical. In this example, we used CSS transforms.

Keyboard interactions

Key(s) Action
Right and Up arrows Increase the selected value by one step
Left and Down arrows Decrease the selected value by one step
Page Up (Optional) increase the value by a set amount greater than one step
Page Down (Optional) decrease the value by a set amount greater than one step
Home Set the slider to the minimum value.
End Set the slider to the maximum value.

For the optional Page Up and Page Down keys, the change in slider value should be by an amount larger than the step changes made by up and down arrows.

Best practices

If the slider is describing the loading progress of a particular region of a page, include the aria-describedby attribute to reference the slider status, and set the aria-busy attribute to true on the region until it is finished loading.

HTML's <input type="range"> implicitly has the role of slider. Do not use aria-valuemax or aria-valuemin attributes on <input type="range"> elements; use min and max instead. Otherwise, any global aria-* attributes and any other aria-* attributes applicable to the slider role.

Prefer HTML

It is recommended to use a native <input> of type range, <input type="range">, rather than the slider role.

Specifications

Specification
Accessible Rich Internet Applications (WAI-ARIA)
# slider

See also