ARIA validation error: Bad value slider for attribute role

Question

I am trying to validate against W3C validator a page that contains:

<button role="slider"></button>

And the validator tells me:

Bad value slider for attribute role on element button

Any idea why? I can't find any explanation in the ARIA specs. I have seen in this blog post that landmark roles are not supported by the validator, but slider is a widget role. Also, another post in the same blog uses the code above as an example...

Simply feeding the code above to the validator allows to reproduce.

Answer 1

The button element has Implicit ARIA Semantics in HTML5. The role must be either button, link, menuitem, menuitemcheckbox, menuitemradio or radio.