The aria-live attribute and the role alert

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Users who navigate using a screen reader are not always aware of changes made on the page. When information is updated or when a message appears, it is sometimes necessary to make the screen reader speak to inform the user. To do this, the ARIA language has the role alert and the attribute aria-live.

The role alert #

Positioned on an HTML element, this allows you to tell the screen reader to vocalize the element automatically when it is created. However, be sure to use this role only in appropriate cases, as clearly stated in the Mozilla MDN documentation. Due to its intrusive nature, role alert should be used sparingly and only in situations where the user's attention is immediately required. Less urgent dynamic changes should use a less aggressive method, such as aria-live="polite" or other live zone roles.

To trigger an alert, several methods are possible, with a support that differ depending on the browser and screen reader pair used. You can read Steve Faulkner's article on this subject.

Here are some examples of methods that are well supported.

Create a new element in the DOM #

You can trigger an alert by inserting a new element in the DOM via Javascript.

  <span role="alert"> This is an alert message. </span>  

Add a role alert on an existing element #

The triggering of an alert can also be done by adding a role="alert" dynamically to an existing element via Javascript.

document.getElementById('alert').setAttribute("role", "alert");

Using innerHTML #

Create an alert via the innerHTML property.

element.innerHTML = '<div role ="alert">This is an alert</div>';

The aria-live attribute #

Positioned on an HTML element, the aria-live attribute is used to indicate to the screen reader that any modification made to its content will result in vocalization by the screen reader.

Three values ​​are possible:

  • Off: no vocalization
  • Polite: the vocalization will take place when the screen reader has finished the current task
  • Assertive: the screen reader interrupts the current task to inform the user

It is strongly recommended that the aria-live attribute be set on the element as soon as the page is loaded to maximize compatibility with different browsers and screen readers.

<span aria-live="polite">5 selected items</span>

Additional attributes allow fine modification of the default behavior of aria-live:

  • aria-atomic: true or false (default), used to indicate whether the whole of the live zone must be read (true) or only the modified part (false).
  • aria-relevant: indicates which type of change triggers a vocalization, possible values: additions (default), removals, all.

Finally, to be complete, know that the ARIA language also provides for some specific roles, status and log in particular which can be useful in certain cases (status bar, logging, chat...) and which, for the moment, must be used in addition to the aria-live attribute to maximize support by the different tools. You can find more info on these roles in the links below.

References #