The required attribute on a <select> tag specifies that an item must be selected before submitting the form.
The form cannot be submitted if the value is empty or null.
A required attribute on a <select> element.
The dropdown must have a value selected before the form can be submitted.
<form action="/tutorial/action.html">
<select name="size" required>
<option value="">-- Select Size --</option>
<option value="small">Small</option>
<option value="medium">Medium</option>
<option value="large">Large</option>
</select><br />
<button type="submit">Submit</button>
</form>
The required attribute specifies that an item must be selected before submitting the form.
As long as the option value is null or is an empty string, the form cannot be submitted.
The required attribute is part of the built-in validation functionality in HTML.
<select required>
Here is when required support started for each browser:
 Chrome
|
1.0 | Sep 2008 |
 Firefox
|
4.0 | Mar 2011 |
 IE/Edge
|
10.0 | Sep 2012 |
 Opera
|
1.0 | Jan 2006 |
 Safari
|
1.0 | Jan 2003 |
