Non-standard: This feature is not standardized. We do not recommend using non-standard features in production, as they have limited browser support, and may change or be removed. However, they can be a suitable alternative in specific cases where no standard option exists.
The :-moz-submit-invalid CSS pseudo-class is a Mozilla extension that represents any submit <button> on forms whose contents aren't valid based on their validation constraints.
By default, no style is applied. You can use this pseudo-class to customize the appearance of the submit button when there are invalid form fields.