An element that displays the progress status for tasks that take a long time.

A progressbar (role) is assigned to the portion of the page that displays the status of a lengthy task. A progress bar indicates that the user's request is received and is in the process of executing the task. Content authors should provide values of aria-valumin, aria-valuemax and aria-valuenow where the aria-valuemax is known. All these values should be updated when the visual content gets updated. The user should be provided with the current status using aria-valuenow. 

Eg: When a file of 100 mb is downloaded, a progressbar indicates aria-valuemin as 0, aria-valuemax as 100 and aria-valuenow with the current status of the download.

If the progressbar is describing the loading progress of a particular region of a page, the author should use aria-describedby to point to the status, and set the aria-busy attribute to true on the region until it is finished loading. It is not possible for the user to alter the value of a progressbar because it is always readonly. 

Note: Assistive technologies generally will render the value of aria-valuenow as a percent of the range between the value of aria-valuemin and aria-valuemax, unlessaria-valuetext is specified. It is best to set the values for aria-valuemin, aria-valuemax, and aria-valuenow in a manner that is appropriate for this calculation.

Microsoft Active Accessibility accRole Property: