How to Write Alt Text That Actually Helps

October 18, 2026 • NOFYI Editorial Team

Alt text is the short description that stands in for an image when the image cannot be seen. A screen reader reads it aloud to a person who cannot see the image, a search engine uses it to understand what the image shows, and a browser shows it when the image fails to load. When alt text is good, the reader gets the same information that a sighted reader gets from the picture. When alt text is missing, vague, or stuffed with keywords, the reader gets noise, or nothing at all.

Writing good alt text is not difficult, but it does require a shift in thinking. You are not describing a file. You are answering a simple question: if this image disappeared, what would the reader need to know? This guide explains how to answer that question in one or two sentences, with a worked example, and with the limits that every writer should know.

What Alt Text Is For

Alt text has three main jobs. The first is accessibility. People who use screen readers rely on alt text to understand images in articles, product pages, charts, and diagrams. If an image carries information, that information should be available in text. If an image is purely decorative, such as a soft background pattern, it should be marked as decorative, usually by leaving the alt attribute empty, so the screen reader can skip it instead of reading a useless description.

The second job is fallback. When an image fails to load because of a slow connection, a broken link, or a blocked file, the browser can show the alt text in its place. A clear description tells the reader what they missed. A file name such as IMG_4829 tells them nothing. The third job is understanding. Search engines and other tools cannot see an image the way a person does. Alt text gives them a plain-language summary of what the image contains, which helps them index and present the page correctly.

Alt text is not a caption, a title, or a place to hide keywords. A caption is visible to everyone and can add context, credit, or a story. Alt text is a replacement for the image itself. A title attribute, when it exists, is extra information shown on hover. Alt text should stand alone. If you read the alt text aloud and a listener can understand the point of the image, the alt text is doing its job.

How to Write Alt Text That Actually Helps

Step 1: Describe What the Image Shows, Not What It Is

Start with the content, not the format. Do not write image of, picture of, or photo of, because the screen reader already tells the listener that it is an image. Instead, name the subject and the action. For a photo of a person, name the person if the identity matters, or describe what they are doing if it does not. For a product photo, name the product and its important visible features, such as colour, size, or material, if those features matter to the reader.

Think about why the image is there. Every image in an article has a purpose. It may show a result, an example, a location, a person, a process, or a comparison. Your alt text should carry that purpose. If the image shows a chart, the purpose is usually the trend or the result, not the colours of the bars. If the image shows a button, the purpose is usually what happens when you press it, not the shape of the button.

Use plain, concrete words. Say a red bicycle leaning against a brick wall, not a nice bike somewhere. Say a bar chart showing sales rising from January to June, not a graph about sales. Concrete words help a listener form a mental picture. Vague

Limitations

Alt text cannot carry everything a complex image contains. A detailed chart, a map, a technical diagram, or a long infographic will need more than one or two sentences. In those cases, alt text should give the main point, and the full detail should live in the surrounding text, in a data table, or in a linked long description. Trying to force a whole diagram into an alt attribute makes the page harder to listen to, not easier.

Alt text also depends on context. The same photo may need different alt text in different articles. A photo of a red bicycle could need alt text about the bicycle in a product article, about the wall behind it in an article about brickwork, or about the street in a travel article. Copying the same alt text everywhere, without thinking about the page, can miss the point. When you reuse an image, check whether the old alt text still matches the new context.

Finally, alt text does not fix a page that relies only on images. If a button is an image with no text, if a menu is an image, or if a whole article is a scanned picture of text, alt text helps but it does not replace real text. Important content should be in real text whenever possible, with images used to support it, not to replace it.

Frequently Asked Questions

How long should alt text be?

Aim for one or two short sentences, often around 125 characters or fewer. If the image needs a longer explanation, keep the alt text short and put the full explanation in the surrounding text, a caption, or a data table.

Should decorative images have alt text?

No. Decorative images that add no information should have empty alt text so screen readers skip them. Describing a divider or a background pattern does not help a listener and it slows down the page.

Can I put keywords in alt text?

Only if they naturally describe the image. Do not stuff a list of search terms into alt text. A listener will hear the list, and it will not help them understand the image. Describe the image in plain words instead.

How do I check alt text with a screen reader?

Read the alt text aloud without looking at the image and ask whether a listener would understand the point of the image. If you can, test the published page with a real screen reader, or ask someone who uses one to listen to the passage and tell you what is missing or repeated.

Conclusion

Good alt text answers one question: if this image disappeared, what would the reader need to know? Describe the image in concrete words, keep it short, do not stuff keywords, and check it by reading it aloud or with a screen reader. In the worked example, a chart became a single clear sentence: Bar chart showing monthly sales rising from January to June, with June as the highest month. That sentence gives a listener the same trend a sighted reader sees, without a list of numbers or a string of keywords. Write alt text that way, and your images will help everyone who visits the page.

words such as beautiful, amazing, or interesting do not add information, even if they feel positive.

Step 2: Keep It Short, Then Stop

Most alt text should be one sentence, or at most two short sentences. A common guideline is to aim for about 125 characters or fewer, not because there is a strict limit, but because screen readers may split longer text and listeners may lose the thread. If you need more than two sentences to explain an image, the image probably contains a lot of information, such as a chart or a diagram. In that case, keep the alt text short and put the full explanation in the surrounding text, in a caption, or in a linked description.

Do not repeat information that is already in the surrounding text. If the paragraph above the image already says that sales rose in June, the alt text does not need to repeat that sentence word for word. It should add the visual detail that the paragraph does not give, or summarise the image in a way that makes sense on its own. Repetition makes listening slower and makes the page feel padded.

Do not stuff keywords into alt text. Writing a list of search terms, such as cheap shoes, best shoes, running shoes, shoes sale, does not help a listener, and it does not help a reader who sees the fallback text. If a keyword belongs in the alt text, it will appear naturally because it describes the image. If it does n

Step 4: Check It With a Screen Reader in Mind

Before you publish, read the alt text aloud without looking at the image. Ask yourself three questions. First, would a listener understand what the image adds to the page? Second, does the alt text repeat the surrounding paragraph? Third, is it short enough to hear in one breath? If the answer to the first question is no, add the missing detail. If the answer to the second is yes, cut the repetition. If the answer to the third is no, split the explanation between the alt text and the body text.

If you can, check the page with an actual screen reader, or ask someone who uses one to listen to the passage. You do not need to test every image on every page to learn from this. Testing one page will show you how your alt text sounds in context, how much repetition you have, and where a short description is not enough. That experience will improve every alt text you write afterwards.

Also check the image in its published form, not just in the editor. Open the page, turn images off in the browser if you can, or use the browser tools to inspect the alt attribute. Confirm that the alt text you wrote is the alt text that was saved, especially for images that were uploaded earlier and reused. A reused image may still carry an old, vague description from its first use.

Worked Example: Alt Text for a Chart Image

Suppose an article includes a simple bar chart. The chart shows monthly sales for a small shop. Sales start low in January, rise slowly through spring, and reach their highest point in June. The paragraph before the chart already says that June was the best month. The chart itself shows the shape of the rise. Here is how to write alt text for it.

First, identify the purpose. The chart is there to show the trend, not to show the colours of the bars or the exact font. The reader needs the trend.

Second, draft a short description. A first draft might be: Bar chart showing monthly sales rising from January to June, with June as the highest month. That is clear, it names the subject, and it gives the result. It is 91 characters, so it is short enough to hear in one breath.

Third, remove repetition and decoration. The paragraph already says June was the best month, but the alt text still needs to stand alone for a listener who jumps straight to the image, so keeping the result is helpful. What you do not need is a list of every monthly value, because those values belong in the article text or in a data table, where a screen reader can navigate them. You also do not need to say bar chart in detail, because the screen reader already announces it as an image, but the words bar chart help a listener understand the form, so they can stay.

Fourth, check the weak version to see the difference. A weak version would be: Chart. That tells the listener nothing. Another weak version would be: Sales chart graph data January February March April May June sales numbers chart. That is keyword stuffing, and it is harder to listen to than the short version. Another weak version would be a paragraph that lists every value and every label. That belongs in the body text, not in the alt attribute.

The final alt text is: Bar chart showing monthly sales rising from January to June, with June as the highest month. It describes the image, it keeps the key result, it stays short, it does not stuff keywords, and it can be checked by reading it aloud without the chart. If a reader later needs the exact numbers, the article should provide them in text or in a table below the chart.

ot describe the image, leave it out.

Step 3: Decide What to Leave Out

Good alt text is as much about what you leave out as what you put in. Leave out the file name, the camera settings, and the technical details, unless they are the point of the image. Leave out the phrase image of. Leave out decorative detail that does not change the meaning. If a photo shows a person in front of a busy street, and the street does not matter, do not list every car, sign, and shop. Focus on the subject and the context that matters.

For decorative images, use empty alt text. A decorative image is one that adds no information, such as a divider, a background texture, or an illustration that repeats what the text already says. In HTML, that is written as alt with nothing between the quotes. In a content system, it usually means leaving the alt field empty and, if the system offers it, marking the image as decorative. The goal is to let the screen reader skip it, not to make the listener hear a description of a pattern they do not need.

For images that are links, describe the destination, not just the picture. If a logo links to the home page, the alt text should say the name of the site and that it links home, or simply the site name if the link purpose is clear from context. If an icon links to a contact page, the alt text should say contact, not envelope icon. The listener needs to know where the link goes, not what the icon looks like.