You can use HTML5's required attribute to make sure users cannot submit a form if certain fields are left empty. This attribute is simple to add and works directly in the browser, giving you an easy way to enforce that important fields are filled out before the form is sent. By placing the required attribute on an input, you tell the browser that this field must have a value.

When you try to submit a form with one or more required fields left blank, the browser will automatically block the submission. It will highlight the empty required fields and show a message, such as "Please fill out this field." This behavior happens before any JavaScript runs, so you do not need to write extra code to prevent the form from submitting if required fields are empty. Using the required attribute gives users instant feedback and helps catch missing input early.