WHO IT HELPS
Read aloud, not seen
Alt text is read out by screen readers and shown if an image does not load or images are switched off. More than two million people in the UK live with sight loss.
See the numbers
WHAT THE GUIDANCE SAYS
Every picture
needs a plan for words.
When a screen reader meets a picture, it reads out the picture's alt text.
If there is none, the meaning is lost. GOV.UK's guidance says good alt text is specific, meaningful and concise, usually no more than two sentences, and that some pictures are better left with none at all.
≤ 2 sentences, as a general aim
Pick a picture type- Say what it means
- Skip 'image of'
- Empty for decoration
- Pictures, in words
THE SHORT ANSWER
Describe the meaning,
not the pixels.
Alt text is read out by screen readers
and shown when an image does not load.
GOOD ALT TEXT
Specific and short
Say what information the image gives, in no more than 2 sentences as a general aim. Do not start with 'Image of' or add things that are not in the picture.
Pick a picture type
CHARTS
Explain the trend
For a chart, GOV.UK says to leave the alt field blank and describe it under the chart, or give a table of the data, as if explaining it over the phone.
Charts and diagrams
FOUR STEPS TO GOOD ALT TEXT
Look, decide,
then describe.
A simple routine based on GOV.UK guidance, for web pages, newsletters and documents.
Ask what the picture is for
Is it informative, or decorative? If it adds no information, give it an empty alt attribute.
Say what it shows that matters
Describe the content and function of the image: specific, meaningful and concise.
Cut the extras
Leave out 'Image of', the photographer's name, anything already on the page and anything not in the image.
Punctuate and stop
Use normal commas and full stops so it reads well aloud, and aim for no more than two sentences.
TWO NUMBERS WORTH KNOWING
Many people need it,
many pages miss it.
One figure on who relies on descriptions,
one on how often the web leaves them out.
53.1%
Top million home pages with images missing alternative text
16.2% of all home page images had no alt text, down from 18.5% in 2025, and 10.8% of images that had it used questionable text such as 'image', 'graphic' or a file name.
THE WEBAIM MILLION · 2026
2 million +
People living with sight loss in the UK
RNIB says more than two million people in the UK live with sight loss, and predicts over four million by 2050. Nearly 80 per cent are 65 or older.
SIGHT LOSS · RNIB
WebAIM notes that automated tools have limits: not every failure can be detected automatically, so the real picture is likely worse.
A QUICK PICTURE CHECK
What kind of
picture is it?
Pick the type of picture to see what GOV.UK guidance says it needs. The bar shows how much description it calls for.
From the GOV.UK Design System guidance on images and GOV.UK content and publishing guidance.
CHARTS AND DIAGRAMS
Tell the story
the chart tells.
GOV.UK's publishing guidance says not to describe a chart too broadly, such as naming only its axes. Explain what is happening in the data and any important trends, as though describing it to someone over the phone.
For a long time series, a description of the trends may be clearer than a table. For diagrams, the guidance asks for a detailed explanation of the processes and relationships in the body text, for people who cannot see the diagram.
Questions
Questions people ask
What is alt text?
Alternative text is a short description of an image. It is read out by screen readers and displayed if an image does not load or if images have been switched off.
Does every image need alt text?
Every image should have the alt attribute, but it can be left empty (alt="") for decorative images and for icons that already have a text label.
How long should alt text be?
GOV.UK's Design System says to aim generally for no more than 2 sentences, and to write anything more complex in a longer text description.
Should alt text start with 'image of'?
No. GOV.UK guidance says not to start with 'Image of' or 'Graphic of', or with common information that would repeat across every image.
How common is missing alt text?
WebAIM's 2026 study of the top million home pages found missing alternative text on 53.1% of them, one of the most common accessibility errors it detected.
Sources
- GOV.UK Design System: Images
- GOV.UK content and publishing guidance: Images
- WebAIM: The WebAIM Million, 2026 report
- RNIB: Key information and statistics on sight loss in the UK
Updated