Bad value “” for attribute “aria-valuenow” on element “div”: The empty string is not a valid floating point number.

The aria-valuenow attribute requires a valid numeric value and cannot be an empty string.

The aria-valuenow attribute is used on range-type widgets like progress bars, sliders, and spinbuttons to indicate the current value. It must be a valid floating point number — for example, 0, 50, or 3.5. An empty string ("") is not a number, so the validator rejects it.

If the current value is unknown or indeterminate, you should remove the aria-valuenow attribute entirely rather than setting it to an empty string. This is common with indeterminate progress bars where the completion percentage isn’t known yet.

When present, aria-valuenow should fall between aria-valuemin and aria-valuemax. All three attributes work together to communicate the state of a range widget to assistive technologies.

Bad Example

<div role="progressbar"
  aria-valuenow=""
  aria-valuemin="0"
  aria-valuemax="100">
  Loading...
</div>

Good Example — Known Value

<div role="progressbar"
  aria-valuenow="50"
  aria-valuemin="0"
  aria-valuemax="100">
  50% complete
</div>

Good Example — Indeterminate State

<div role="progressbar"
  aria-valuemin="0"
  aria-valuemax="100">
  Loading...
</div>

In the indeterminate example, omitting aria-valuenow tells assistive technologies that the progress is ongoing but the exact value is not known.

Learn more:

MDN Reference

MDN Web Docs: aria-valuenow

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MDN Reference

MDN Web Docs: ARIA - Using the progressbar role

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MDN Reference

MDN Web Docs: ARIA - Using the slider role

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