The read-only rangeOverflow property of a ValidityState object indicates if the value of an <input>, after having been edited by the user, does not conform to the constraints set by the element's max attribute.
If the field is numeric in nature, including the date, month, week, time, datetime-local, number and range types and a max value is set, if the value doesn't conform to the constraints set by the max value, the rangeOverflow property will be true.
Given the following:
html
<input type="number" min="20" max="40" step="2" />
if value > 40, rangeOverflow will be true. When true, the element matches the :invalid and :out-of-range CSS pseudo-classes.