They need to all have the same name.

All radio buttons have to have the same name:

<input type='radio' name='foo'>

Only 1 radio button of each group of buttons with the same name can be checked.

Give them the same name, and it will work. By definition Radio buttons will only have one choice, while check boxes can have many.

<input type="radio" name="Radio1" />

Add “name” attribute and keep the name same for all the radio buttons in a form.

i.e.,

<input type="radio" name="test" value="value1"> Value 1
<input type="radio" name="test" value="value2"> Value 2
<input type="radio" name="test" value="value3"> Value 3

Hope that would help.

Just give them the same name throughout the form you are using.

<form><input type="radio" name="selection">
      <input type="radio" name="selection">
      ..
      ..
</form>

All the radio buttons options must have the same name for you to be able to select one option at a time.

Only one Step you need to follow!

Make Sure you need to add the attribute name in the opening tag with the same values of that attribute name!

Example :

<input name="18+" value="yes" id="18" type="radio">Yes
  <input name="18+" value="No" id="bel" type="radio">No