<input type="radio">

<input> elements of type radio are generally used in radio groups—collections of radio buttons describing a set of related options. Only one radio button in a given group can be selected at the same time. Radio buttons are typically rendered as small circles, which are filled or highlighted when selected.

<input type="radio" id="radioButton">

They are called radio buttons because they look and operate in a similar manner to the push buttons on old-fashioned radios, such as the one shown below.

The value attribute

The value attribute is a DOMString containing the radio button's value. The value is never shown to the user by their user agent. Instead, it's used to identify which radio button in a group is selected.

Defining a radio group

A radio group is defined by giving each of radio buttons in the group the same name. Once a radio group is established, selecting any radio button in that group automatically deselects any currently-selected radio button in the same group.

You can have as many radio groups on a page as you like, as long as each has its own unique name.

For example, if your form needs to ask the user for their preferred contact method, you might create three radio buttons, each with the name property set to "contact" but one with the value "email", one with the value "phone", and one with the value "mail". The user never sees the value or the name (unless you expressly add code to display it).

The resulting HTML looks like this:

<form>
  <p>Please select your preferred contact method:</p>
  <div>
    <input type="radio" id="contactChoice1"
     name="contact" value="email">
    <label for="contactChoice1">Email</label>

    <input type="radio" id="contactChoice2"
     name="contact" value="phone">
    <label for="contactChoice2">Phone</label>

    <input type="radio" id="contactChoice3"
     name="contact" value="mail">
    <label for="contactChoice3">Mail</label>
  </div>
  <div>
    <button type="submit">Submit</button>
  </div>
</form>

Here you see the three radio buttons, each with the name set to "contact" and each with a unique value that uniquely identifies that individual radio button within the group. They each also have a unique id, which is used by the <label> element's for attribute to associate the labels with the radio buttons.

You can try out this example here:

Data representation of a radio group

When the above form is submitted with a radio button selected, the form's data includes an entry in the form "contact=name". For example, if the user clicks on the "Phone" radio button then submits the form, the form's data will include the line "contact=phone".

If you omit the value attribute in the HTML, the submitted form data assigns the value "on" to the group. In this scenario, if the user clicked on the "Phone" option and submitted the form, the resulting form data would be "contact=on", which isn't helpful. So don't forget to set your value attributes!

It's fairly uncommon to actually want to allow the form to be submitted without any of the radio buttons in a group selected, so it is usually wise to have one default to the "checked" state. See Selecting a radio button by default below.

Let's add a little bit of code to our example so we can examine the data generated by this form. The HTML is revised to add a <pre> block to output the form data into:

<form> 
  <p>Please select your preferred contact method:</p>
  <div>
    <input type="radio" id="contactChoice1"
           name="contact" value="email">
    <label for="contactChoice1">Email</label>
    <input type="radio" id="contactChoice2"
           name="contact" value="phone">
    <label for="contactChoice2">Phone</label>
    <input type="radio" id="contactChoice3"
           name="contact" value="mail">
    <label for="contactChoice3">Mail</label>
  </div>
  <div>
    <button type="submit">Submit</button>
  </div>
</form>
<pre id="log">
</pre>

Then we add some JavaScript to set up an event listener on the submit event, which is sent when the user clicks the "Submit" button:

var form = document.querySelector("form");
var log = document.querySelector("#log");

form.addEventListener("submit", function(event) {
  var data = new FormData(form);
  var output = "";
  for (const entry of data) {
    output = entry[0] + "=" + entry[1] + "\r";
  };
  log.innerText = output;
  event.preventDefault();
}, false);

Try this example out and see how there's never more than one result for the "contact" group.

Using radio inputs

We already covered the fundamentals of radio buttons above. Let's now look at the other common radio-button-related features and techniques you may need to know about.

Selecting a radio button by default

To make a radio button selected by default, you simply include checked attribute, as shown in this revised version of the previous example:

<form>
  <p>Please select your preferred contact method:</p>
  <div>
    <input type="radio" id="contactChoice1"
     name="contact" value="email" checked>
    <label for="contactChoice1">Email</label>

    <input type="radio" id="contactChoice2"
     name="contact" value="phone">
    <label for="contactChoice2">Phone</label>

    <input type="radio" id="contactChoice3"
     name="contact" value="mail">
    <label for="contactChoice3">Mail</label>
  </div>
  <div>
    <button type="submit">Submit</button>
  </div>
</form>

In this case, the first radio button is now selected by default.

Providing a bigger hit area for your radio buttons

In the above examples, you may have noticed that you can select a radio button by clicking on its associated <label> element, as well as on the radio button itself. This is a really useful feature of HTML form labels that makes it easier for users to click the option they want, especially on small-screen devices like smartphones.

Beyond accessibility, this is another good reason to properly set up <label> elements on your forms.

Validation

Radio buttons don't participate in constraint validation; they have no real value to be constrained.

Styling radio inputs

The following example shows a slightly more thorough version of the example we've seen throughout the article, with some additional styling, and with better semantics established through use of specialized elements. The HTML looks like this:

<form>
  <fieldset>
    <legend>Please select your preferred contact method:</legend>
    <div>
      <input type="radio" id="contactChoice1"
       name="contact" value="email" checked>
      <label for="contactChoice1">Email</label>

      <input type="radio" id="contactChoice2"
       name="contact" value="phone">
      <label for="contactChoice2">Phone</label>

      <input type="radio" id="contactChoice3"
       name="contact" value="mail">
      <label for="contactChoice3">Mail</label>
    </div>
    <div>
      <button type="submit">Submit</button>
    </div>
  </fieldset>
</form>

There's not much new to note here except for the addition of <fieldset> and <legend> elements, which help to group the functionality nicely and in a semantic way.

The CSS involved is a bit more significant:

html {
  font-family: sans-serif;
}

div:first-of-type {
  display: flex;
  align-items: flex-start;
  margin-bottom: 5px;
}

label {
  margin-right: 15px;
  line-height: 32px;
}

input {
  -webkit-appearance: none;
  -moz-appearance: none;
  appearance: none;

  border-radius: 50%;
  width: 16px;
  height: 16px;

  border: 2px solid #999;
  transition: 0.2s all linear;
  outline: none;
  margin-right: 5px;

  position: relative;
  top: 4px;
}

input:checked {
  border: 6px solid black;
}

button,
legend {
  color: white;
  background-color: black;
  padding: 5px 10px;
  border-radius: 0;
  border: 0;
  font-size: 14px;
}

button:hover,
button:focus {
  color: #999;
}

button:active {
  background-color: white;
  color: black;
  outline: 1px solid black;
}

Most notable here is the use of the appearance property (with prefixes needed to support some browsers). By default, radio buttons (and checkboxes) are styled with the operating system's native styles for those controls. By specifying appearance: none, you can remove the native styling altogether, and create your own styles for them. Here we've used a border along with border-radius and a transition to create a nice animating radio selection. Notice also how the :checked pseudo-class is used to specify the styles for the radio button's appearance when selected.

This is not without its problems: appearance is not too bad for simple styling, but it tends to behave inconsistently in some browsers, and it doesn't work at all in Internet Explorer. Test carefully to make sure your site works in every browser for which you want users or customers.

Notice that when clicking on a radio button, there's a nice, smooth fade out/in effect as the two buttons change state. In addition, the style and coloring of the legend and submit button are customized to have strong contrast. This might not be a look you'd want in a real web application, but it definitely shows off the possibilities.

Specifications

Browser compatibility

See also

• <input> and the HTMLInputElement interface that implements it.
• RadioNodeList: the interface that describes a list of radio buttons