### [Adding Validation to the Number Slider Field (Single Page and Multi Page Forms)](https://wpforms.com/developers/adding-validation-to-the-number-slider-field-single-page-and-multi-page-forms/) **Published:** September 8, 2025 **Author:** Umair Majeed **Content:** Would you like to require a value in the Number Slider field or stop users from moving to the next page until a minimum value is selected? The Number Slider does not include a Required option, but you can add custom validation. In this tutorial, we’ll show server-side validation for single-page forms and client-side validation for multi-page forms that blocks page changes until a valid value is selected. If you need help adding code, please see our tutorial on [adding custom PHP snippets](https://wpforms.com/developers/how-to-add-custom-php-or-javascript-for-wpforms/). ## Server-Side: Validate on Submit (best for single-page forms) This snippet uses the `wpforms_process_validate_number-slider` action to check the slider value after submission. If the submitted value is `0` (or below your threshold), it adds a field error and prevents the entry from being saved. This validation runs after the entire form is submitted. On multi-page forms, this shows an error only after the final submit. It does not block moving between pages. ## Client-Side: Block Page Change (best for multi-page forms) For multi-page forms, validate in the browser before the form moves to the next page. This snippet outputs a small script that listens for the `wpformsBeforePageChange` event and stops the page change if the slider value is below your minimum. That’s it. Now you know how to validate Number Slider field for single and multi-page forms. **Categories:** Tutorials, Fields ---