Press & Media - Drinking Water Inspectorate

Security and Emergencies - Drinking Water Inspectorate

Who we are - Drinking Water Inspectorate

Research Programme - Drinking Water Inspectorate

Water Companies - Drinking Water Inspectorate

Accessibility Statement - Drinking Water Inspectorate

Contact us - Drinking Water Inspectorate

Page not found - Drinking Water Inspectorate

Help - Drinking Water Inspectorate

What's new - Drinking Water Inspectorate

Form controls must appear sufficiently distinct from their surroundings, so that people 
with visual impairments are still able to clearly see them.    

Either the border or the form control itself must have a 3:1 colour contrast with the 
surrounding area. 

## Methodology

* All `<input>`, `<textarea>`, and `<select>` elements are checked.
* For `<input>` elements, these types are ignored as their
  appearance is controlled by the browser or operating system:
  `checkbox`, `radio`, `submit`, `reset`, `image`, `hidden`, `file`. 
* The flattened background color of the control is determined. This is the color of the
  control itself, combined with any parent elements if the control is transparent.
* If the control has a border or outline:
  * The flattened background color of each edge is determined. 
    This is the color of the edge itself, combined with any parent elements
    if the edge is transparent.
  * If any edge has sufficient contrast with the flattened background color of the control, 
    the control is considered to have sufficient contrast.
* If the control does not have a border or outline:
  * The flattened background color of the surrounding 
    area is determined. This is the color of the first control's parent element which is at least 
    one pixel larger around the element in every dimension, i.e. above, below, left, and right.
  * If the background color of the element has sufficient contrast with surrounding area color
    the control is considered to have sufficient contrast.

## Troubleshooting

There are some limitations to the contrast checker:

* The use of drop shadows, glowing effects, gradients, and other complex effects 
  mean there is no one clear color to determine the contrast ratio against. 
  In these cases, the contrast ratio cannot currently be determined.
* It is possible for an element to be positioned over multiple elements, e.g. via
  `position: absolute` or `position: fixed`. In this case, the contrast ratio cannot 
  currently be determined.

## Further reading

* [WCAG 1.4.11](https://www.w3.org/WAI/WCAG21/Understanding/non-text-contrast.html)

non-text-contrast

August 2025

July 2025

Drinking Water Inspectorate

Title / URL	Issues
Press & Media - Drinking Water Inspectoratewww.dwi.gov.uk/press-media/	1
Security and Emergencies - Drinking Water Inspectoratewww.dwi.gov.uk/semd/	1
Who we are - Drinking Water Inspectoratewww.dwi.gov.uk/who-we-are/	1
Research Programme - Drinking Water Inspectoratewww.dwi.gov.uk/research/research-programme/	1
Water Companies - Drinking Water Inspectoratewww.dwi.gov.uk/water-companies/	1
Accessibility Statement - Drinking Water Inspectoratewww.dwi.gov.uk/accessibility-statement/	1
Contact us - Drinking Water Inspectoratewww.dwi.gov.uk/what-we-do/contact-us/	1
Page not found - Drinking Water Inspectoratewww.dwi.gov.uk/invented-url-for-404-page	1
Help - Drinking Water Inspectoratewww.dwi.gov.uk/help/	1
What's new - Drinking Water Inspectoratewww.dwi.gov.uk/whats-new/	1

Ensure form controls contrast sufficiently with their surroundings

Drinking Water Inspectorate

Where this issue has occurred