I've just discovered that Google forms allows radio buttons to be checked, then unchecked by clicking on them a second time:
Do you know of any valid uses of this? It would be helpful to do some UX research into it.
And do you know if it's been documented anywhere? Their own Material Design v3 guidelines explicity disallow this: "Once selected, there is always one radio button selected in the group, users can change their selection but they can’t unselect."
The whole purpose of Radio buttons is to make a single selection only.
But I can see a potential use case for this behaviour. Consider a form where there are some optional questions, a user might accidentally click on one of these options and then there is no way to deselect in case they realise that they do not wish to answer this question.
I have never observed this behaviour in any design system.
I have created various form for online tools and have always opted for clear selection button or None/I don't wish to answer as an option to provide flexibility.
Possible reason why Google opted for this approach
Would love to hear more on this behaviour.
It turns out that Jotform doesn't allow un-checking (it treats radio buttons the standard HTML way):
Interesting note: it doesn't provide a "none of the above" option by default, resulting in radio button questions acting like required fields when an option is checked.
Typeform on the other hand does allow unchecking in their own version of radio buttons:
