:default

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since January 2020.

The :default CSS pseudo-class selects form elements that are the default in a group of related elements.

Try it

label,
input[type="submit"] {
  display: block;
  margin-top: 1em;
}

input:default {
  border: none;
  outline: 2px solid deeppink;
}

<form>
  <p>How did you find out about us?</p>
  <label
    ><input name="origin" type="radio" value="google" checked /> Google</label
  >
  <label><input name="origin" type="radio" value="facebook" /> Facebook</label>
  <p>Please agree to our terms:</p>

  <label
    ><input name="newsletter" type="checkbox" checked /> I want to subscribe to
    a personalized newsletter.</label
  >

  <label
    ><input name="privacy" type="checkbox" /> I have read and I agree to the
    Privacy Policy.</label
  >

  <input type="submit" value="Submit form" />
</form>

What this selector matches is defined in HTML Standard §4.16.3 Pseudo-classes — it may match the <button>, <input type="checkbox">, <input type="radio">, and <option> elements:

A default option element is the first one with the selected attribute, or the first enabled option in DOM order. multiple <select>s can have more than one selected option, so all will match :default.
<input type="checkbox"> and <input type="radio"> match if they have the checked attribute.
<button> matches if it is a <form>'s default submission button: the first <button> in DOM order that belongs to the form. This also applies to <input> types that submit forms, like image or submit.

Syntax

:default {
  /* ... */
}

Examples

HTML

<fieldset>
  <legend>Favorite season</legend>

  <input type="radio" name="season" id="spring" value="spring" />
  <label for="spring">Spring</label>

  <input type="radio" name="season" id="summer" value="summer" checked />
  <label for="summer">Summer</label>

  <input type="radio" name="season" id="fall" value="fall" />
  <label for="fall">Fall</label>

  <input type="radio" name="season" id="winter" value="winter" />
  <label for="winter">Winter</label>
</fieldset>

CSS

input:default {
  box-shadow: 0 0 2px 1px coral;
}

input:default + label {
  color: coral;
}

Result

Specifications

Specification
HTML # selector-default
Selectors Level 4 # default-pseudo

Browser compatibility

	Desktop					Mobile
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet	WebView Android
`:default`	10	79	4	10	5	18	4	10.1	5	1.0	37