In short
Alt text should convey the image's purpose in its context, not catalogue its contents. Decorative images take an empty alt attribute so screen readers skip them, which is different from omitting the attribute. An image that is a link describes the destination, and an image carrying data — a chart or a screenshot — needs the finding it conveys, not a description of its appearance.
Purpose, not description
The question is not "what is in this image?" It is "what would someone miss if it were not here?"
The same photograph of a workshop needs different alt text depending on its job. On an about page illustrating the studio, it might be decorative. In an article about workspace layout, the arrangement is the point. In a case study, the client's premises is the point.
This is why alt text cannot be generated well without context, and why bulk-adding it produces text that is technically present and practically useless.
Empty alt is correct for decoration
An image adding nothing to the content — a background texture, a divider, a stock photograph beside text that already says everything — should have alt="".
That is an explicit instruction to skip it, and it is the right answer surprisingly often.
Empty alt is not the same as missing alt. With no attribute at all, some screen readers read the filename, which is usually worse than silence — IMG_20260403_final_v2.jpg announced mid-paragraph helps nobody.
So: decorative gets alt="". Meaningful gets a description. Neither gets nothing.
Images that are links
When an image is inside a link, the alt text becomes the link text. So it should describe the destination, not the picture.
A logo linking home is alt="Troiana, home", not alt="Troiana logo". A product photograph linking to the product is the product name.
If the link also contains text saying the same thing, the image should be alt="" — otherwise the destination is announced twice, which is a common and irritating duplication.
Charts, diagrams and data
This is where alt text most often fails, because people describe the appearance rather than the information.
"Bar chart showing revenue" tells a screen reader user only that they are missing something. Give them the finding: "Revenue rose from €40k to €112k between January and June, with the largest increase in April."
For complex diagrams, a short alt plus a longer description in the surrounding text works better than a very long alt attribute. The prose serves everyone — sighted readers frequently miss the point of a chart too — and this is one of the places where writing for accessibility improves the page generally.
If a chart's data matters, consider putting the numbers in an accessible table alongside it.
Screenshots
In documentation and tutorials, screenshots usually carry instructions.
Describe what the reader needs to see and do, not the interface's appearance. Not "screenshot of the settings page" but "the Notifications section, with the Email digest toggle switched on."
If the screenshot contains text that matters, that text needs to exist outside the image too. Text in an image is invisible to screen readers, to search engines, and to anyone using translation.
Practical rules
Do not start with "image of" or "picture of." Screen readers already announce that it is an image.
Keep it to a sentence or so where possible. If it needs a paragraph, that content probably belongs in the page.
Do not stuff keywords. Alt text is read aloud to real people; a phrase written for search reads as gibberish and helps neither audience.
Punctuate it. It is read as speech, and a full stop creates a pause.
Do not repeat the caption. If a caption already describes the image, the alt can be empty or brief — otherwise the same text is announced twice.
Photographs of people
Describe what is relevant to the context. In a team page, the person's name is the point. In an article about an event, what is happening matters more than who is there.
Avoid describing appearance, ethnicity or age unless it is genuinely relevant to why the image is present. It usually is not, and guessing is both unhelpful and presumptuous.
A workable test
Read the page aloud, replacing each image with its alt text. Does it still make sense? Does anything sound redundant, or leave a gap?
That five-minute check catches nearly everything: the missing description, the duplicated caption, the decorative image being announced at length, and the chart whose point was never written down.
If you have a large library of images with no alt text and are wondering where to start, start with the ones inside links and the ones carrying data — book a call if you want a hand prioritising.
Common questions
What should alt text say?
What someone would miss if the image were not there, in its specific context — not a catalogue of the contents. The same photograph needs different alt text on different pages, which is why bulk-generated alt text tends to be technically present and practically useless.
When should alt text be empty?
When the image is decorative and adds nothing to the content — a texture, a divider, or a stock photo beside text that already says everything. Use alt="" explicitly, which instructs screen readers to skip it. Omitting the attribute entirely is different and worse, since some readers then announce the filename.
How do I write alt text for a chart?
Give the finding rather than the appearance. 'Bar chart showing revenue' tells a screen reader user only that they are missing something; 'Revenue rose from €40k to €112k between January and June' conveys the point. For complex charts, use a short alt plus a fuller description in the surrounding text.
What alt text should an image link have?
A description of the destination, since the alt text becomes the link text. A logo linking home is 'Troiana, home' rather than 'Troiana logo'. If adjacent text already names the destination, the image should have empty alt so it is not announced twice.
Should alt text include keywords for SEO?
No. Alt text is read aloud to real people, so a phrase written for search engines reads as gibberish and serves neither audience. Describe the image's purpose accurately — if a relevant term appears naturally that is fine, but stuffing is counterproductive.
