Alumni Ambassadors • City, University of London

News • City, University of London

Events • City, University of London

All Degree, Foundation & Short Courses • City, University of London

Apprenticeships • City, University of London

Research case studies • City, University of London

Funding options • City, University of London

Research centres and groups • City, University of London

Researcher development • City, University of London

Fund your business • City, University of London

All controls on the page - including links, buttons, and fields - should clearly 
indicate when they have been selected by the keyboard.

This is a stricter version of [WCAG 2.4.7](https://www.w3.org/WAI/WCAG21/Understanding/focus-visible.html),
which requires that the focus indicator is visible, but doesn't specify how clearly
it should be visible.

You can confirm this yourself by loading a webpage and using the Tab key to navigate 
through it. Anything you can select should clearly alter its appearance when selected. 
For example, a text field might change color, or have a distinctive border applied. 

## The requirements

The [official requirements](https://w3c.github.io/wcag/understanding/focus-appearance.html) are 
complicated. A simplified version is:

* Surround the control with a solid outline
* The outline must have at least 3:1 contrast with its background
* The outline must have at least 3:1 contrast with its surroundings, or be at least 2px thick

The actual requirements allow for more variation, but generally require that you 
calculate the perimeter and/or area of the focus area, which can be very difficult.

## How to fix

Links and form controls should use a focus selector which contrasts with their
unfocused state, as well as any surroundings of the focus state. 

In practice, the easiest way to accomplish this is to use a two-color focus, like so:

```css
/* ensure high-contrast mode still has an indicator */
outline: 2px transparent solid;

/* Apply a thick yellow box-shadow with 
   a thin dark blue indicator in the middle */
box-shadow: 0 0 0 2px #F9F9D1, 0 0 0 4px #396196, 0 0 4px 8px #F9F9D1;
``` 

From [Technique C40](https://www.w3.org/WAI/WCAG22/Techniques/css/C40).

Using two contrasting colors guarantees that the focus state will be visible, 
regardless of the background or surrounding colors.

## Troubleshooting

### Elements appear to change in the browser

Focus states should be defined in CSS alone, and not require JavaScript to work. 

Try disabling JavaScript on the page, and see if focus is still visible. If it not, 
then the focus state won't work with assistive technologies that don't have a physical
keyboard, e.g. mobile phones.

Some more unusual means of implementing a focus state cannot be detected or measured
automatically. These include:

* Focus implemented via pseudo-elements - such as `::after` or `::before`. 
* Focus using `:focus-within` (JavaScript current provides no way to access these).
* Focus cascaded to child elements, e.g. a `<span>` inside an `<a>` tag. We detect
  some of these cases, but there are variations that we cannot detect.

Currently, there is no practical way to assess these focus states automatically.

### Elements over images not analyzed

Silktide cannot assess the contrast of elements that are over images. This is because
the contrast of an element is calculated by comparing the color of the element with the
color of the background. 

If the element is over an image, the background color is the
color of the image, which varies from pixel-to-pixel, and may vary further as the page
is resized, due to responsive design.

### Unexpected elements are focusable

You may be surprised to see tags like `<div>` or `<span>` being shown as focusable.
If an element has a `tabindex` of 0 or higher, it becomes focusable. Any HTML tag can be made 
focusable in this way, this is so that custom controls (e.g. your own drop-down menus, or 
sliders) can support keyboard navigation. [Learn more about tabindex on MDN](https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/tabindex).

## Further reading

This is part of the draft WCAG 2.2 specification and is subject to change.

* [WCAG 2.4.11](https://w3c.github.io/wcag/understanding/focus-appearance.html)

ensure-focus-appearance

February 2025

January 2025

City University of London

Title / URL	Issues
Alumni Ambassadors • City, University of Londonwww.city.ac.uk/alumni/networks/ambassadors	2
News • City, University of Londonwww.city.ac.uk/news-and-events/news	2
Events • City, University of Londonwww.city.ac.uk/news-and-events/events	2
All Degree, Foundation & Short Courses • City, University of Londonwww.city.ac.uk/prospective-students/courses	2
Apprenticeships • City, University of Londonwww.city.ac.uk/prospective-students/courses/apprenticeships	2
Research case studies • City, University of Londonwww.city.ac.uk/research/impact/case-studies	2
Funding options • City, University of Londonwww.city.ac.uk/prospective-students/finance/funding	2
Research centres and groups • City, University of Londonwww.city.ac.uk/research/centres	2
Researcher development • City, University of Londonwww.city.ac.uk/research/support/researcher-development	1
Fund your business • City, University of Londonwww.city.ac.uk/business/grow/funding	1

Ensure controls clearly indicate when they are selected

City University of London

Where this issue has occurred