CONTRAST
At least 4.5 to 1
Under WCAG level AA, normal text needs a contrast ratio of at least 4.5:1 against its background. Large text needs at least 3:1.
Check your textREADABLE TEXT IN PLAIN ENGLISH
Make the words
stand out.
Pale grey text on white looks elegant and reads badly.
4.5 : 1 the everyday minimum
4.5:1 Contrast for normal-sized text
- Dark on light, clearly
- Bigger text, gentler rule
- Zoom without breaking
- Small numbers, readable pages
The Web Content Accessibility Guidelines set measurable rules for text: how much contrast it needs against its background, and how far it must zoom without breaking. UK public sector sites are expected to meet them, and any site can use them.
THE SHORT ANSWER
Contrast, size
and zoom.
Three checks catch most unreadable text.
All three are measurable.
GLARE AND EYESIGHT
Who it helps
Low contrast hits people with sight impairments hardest. The GOV.UK guidance notes that a colour-contrast fix is a low-cost change that helps a lot of people.
See the numbers
ZOOM
200% and still working
Every feature should work when text size is increased by 200%, and content should reflow into a single column at 400%.
Test a pageA QUICK CONTRAST CHECK
What text are
you checking?
Pick a case to see the minimum contrast ratio WCAG sets. The bar shows how demanding the requirement is.
Ratios from the University of Washington's accessible technology guide and the CMS Section 508 tip sheet, both summarising WCAG. General information, not legal advice.
FOUR QUICK TESTS
Check text
in minutes.
No special training is needed for a first pass. These follow the published guidance.
Run a contrast checker
Free tools take two colours and report the ratio with a pass or fail for each WCAG level.
Zoom to 200%
Increase text size by 200% and check that every feature still works and nothing is cut off.
Push to 400%
At 400% the content should reflow into a single column rather than needing sideways scrolling.
Don't rely on colour
Never use colour as the only way to explain or distinguish something, such as a required field.
TWO NUMBERS WORTH KNOWING
Built for
more people.
One ratio that sets the everyday minimum,
one figure on who benefits.
4.5:1
Contrast for normal-sized text
Text under 18 point, or under 14 point bold, needs a foreground-to-background contrast ratio of at least 4.5 to 1. Images of text count too, the CMS Section 508 programme notes.
MINIMUM · WCAG LEVEL AA
1 in 5
People in the UK with a long-term condition or disability
GOV.UK says at least 1 in 5 people in the UK have a long-term illness, impairment or disability, and many more have a temporary disability.
WHO BENEFITS · GOV.UK
GOV.UK lists poor colour contrast that makes text hard to read among the common problems with public sector websites, alongside sites that are hard to use on mobile or by keyboard.
WHO HAS TO DO THIS
A standard,
and a law for some.
In the UK, public sector websites and apps are expected to meet WCAG 2.2 at level AA, under the public sector accessibility regulations. GOV.UK points out that these build on duties under the Equality Act 2010.
Other organisations are not all covered by those regulations, but all UK service providers have a duty to make reasonable adjustments for disabled people. The WCAG contrast rule did not change between versions 2.1 and 2.2.
Questions
Questions people ask
What is a contrast ratio?
It measures how strongly the text colour stands out from its background colour. Free checkers calculate it from the two colours, and WCAG sets minimums such as 4.5:1 for normal text at level AA.
What counts as large text?
WCAG treats text of 18 point or larger, or 14 point bold or larger, as large. Large text has a lower minimum contrast ratio, 3:1 at level AA.
Is pale grey text on white accessible?
Often not. Light lettering on a bright background is one of the combinations the CMS Section 508 programme warns leaves low-vision users significantly disadvantaged. Check it with a contrast tool.
Does zoom really matter?
Yes. GOV.UK guidance says every feature should work at 200% text size and content should reflow to a single column at 400%.
Do these rules apply to my website?
UK public sector websites and apps must meet WCAG 2.2 AA under the accessibility regulations, with some exceptions. Other providers have Equality Act duties. This page is general information, not legal advice.
Where the facts come from
Updated