Radio
Allows selection of a single item in a group of options.
If requiring multi-selection, please consider checkboxes or listbox instead.
HTML gives us native radio buttons that are fully accessible by default. Unfortunately, the look-and-feel of these controls is often at odds with a web site's design system or branding guidelines. This issue is compounded by the fact that native radio buttons are traditonally very difficult to re-style.
Our pattern shows how modern CSS and SVG can be used to create a custom facade over the native radio buttons, while maintaining accessibility requirements.
Updated: July 6th, 2018
You can get a quick idea of the required markup structure by viewing our bones project.
You can take a look at the custom radio group pattern in action on our examples site.
You can see a real life working example in our Skin CSS Framework.
Radio buttons must be grouped together and a group must contain at least two radio buttons.
Each group of radio buttons must be labelled.
Each individual radio button must be labelled.
Radio buttons must belong inside of a form element, and that form element must have a submit button.
Toggling a radio should not cause an app update until the related form is submitted by the user. If instant app updates are required, perhaps consider the switch pattern or a button-less menu.
This section provides interaction design for keyboard, screen reader and pointing devices.
Tabbing into the group will set focus on the currently checked radio button. If no button is currently checked, focus will move to the first button or the last depending on whether TAB or SHIFT+TAB was used to enter the group.
TAB and SHIFT+TAB will leave the radio button group.
RIGHT ARROW and DOWN ARROW will focus and select the next button in group.
LEFT ARROW and UP ARROW will focus and select the previous button in the group.
SPACEBAR selects the currently focussed radio button.
ENTER submits the form that the radio group belongs to.
Radio must be reachable with screen reader (even when disabled).
Radio must be announced as "Radio".
Radio label must be announced.
Radio group label, if applicable, must be announced.
Radio state must be announced (checked or unchecked).
Clicking radio must toggle the checked state.
Clicking radio label must toggle the checked state.
Our sample implementation follows the Progressive Enhancement strategy; we build in a layered fashion that allows everyone to access the basic content and functionality of a web page.
The three layers are:
Content (HTML)
Presentation (CSS)
Behaviour (JS) (not required)
Our radio buttons will be fully visible and operable in an HTML-only state, an HTML+CSS state, and an HTML+CSS+JavaScript state.
Native HTML radio buttons are 100% accessible by default and support features such as form data, form reset and form complete.
Native HTML radio buttons should always be your baseline starting point.
<fieldset><legend>Listing Format</legend><span><input id="lf_all" type="radio" name="lf" value="all" /><label for="lf_all">All Listings</label></span><span><input id="lf_auction" type="radio" name="lf" value="auction" /><label for="lf_auction">Auction</label></span><span><input id="lf_bin" type="radio" name="lf" value="bin" /><label for="lf_bin">Buy it Now</label></span></fieldset>
The fieldset creates the grouping semantics. The legend creates the group label.
Each input and label pair are further grouped inside a span container. This span container can be replaced with a div for vertical stacking of radio buttons.
Native HTML radio buttons are 100% accessible by default, but may not match your design system look & feel.
We will now show how CSS and SVG can give you the visuals you desire, without any JavaScript.
We are going to:
Hide the native radio button
Display one of two custom icons (checked or unchecked) in it's place
Assign a focus outline to the custom icon
We need to create a new container element that will host each radio button and it's icon. We give it a class of radio:
<span class="radio"><input class="radio__control" id="lf_all" type="radio" name="lf" value="all" /><!-- icon goes here --></span>
For convenience, we also add a .radio__control BEM element modifier to each input tag.
We make the native input invisible, and keep it in place, using opacity and absolute positioning:
.radio__control {opacity: 0;position: absolute;z-index: 1;}
We keep the radio in place, so that we can continue to click on it. Although invisible, it is still the native input that receives click and focus events. This is important so that the underlying input maintains all built-in event handling and state.
Remember, clicking the label of a radio button will also toggle the checked state.
We need two icons: checked and unchecked.
We have mentioned that SVG will be used to create the icon. We actually have two implementation choices when it comes to our SVG:
background SVG
foreground SVG
Here's how the markup will look with background SVG:
<span class="checkbox"><input id="lf_all" type="radio" name="lf" value="all" /><span class="radio__icon"></span></span>
And here's how the markup will look with foreground SVG:
<span class="radio"><input id="lf_all" type="radio" name="lf" value="all" /><span class="radio__icon" hidden><svg aria-hidden="true" class="radio__unchecked" focusable="false"><use xlink:href="#icon-radio-unchecked"></use></svg><svg aria-hidden="true" class="radio__checked" focusable="false"><use xlink:href="#icon-radio-checked"></use></svg></span></span>
This markup assumes that the symbol definitions for #icon-radio-unchecked and #icon-radio-checked exist on the page.
The hidden attribute ensures that the SVG icon is not visible if the page is in a non-CSS state; it also helps prevent a flash of unstyled content (FOUC).
As you can see, the background SVG markup is more concise, however it has two issues to be aware of:
the color of the icon is not changeable with CSS
alternate variations are needed for windows high contrast mode
On the other hand, foreground SVG has neither of these issues.
Remember that the keyboard will always focus on the real, native input. However, we cannot see the real focus indicator because the element has 0 opacity. To workaround this, we can create a custom focus outline around the SVG element:
.radio__control:focus + .radio__icon {outline: 1px dotted #767676;}
A dotted border is a good choice, mimicking that of various browsers (such as Firefox).
This section gives an overview of our use of ARIA, within the specific context of the radio pattern.
Removes the presentational SVG element from the accessibility tree.
July 6th 2018: Added details for SVG icon.
