HTML <input> required Attribute Definition and Usage:
The required attribute is a boolean attribute.
When present, it specifies that an input field must be filled out before submitting the form.
Note: The required attribute works with the following input types: text, tel, email, password, date pickers, number, checkbox, radio, search, URL, and file.

Syntax:-

<input required>

An example of an HTML form with a required input field is as follows:

<form action="https://www.slightbook.com/">
  <label for="bookname">bookname:</label>
  <input type="text" id="bookname" name="bookname" required>
  <input type="submit">
</form>