How to Write Alt Text People Can Use

Alt text is the short description a screen reader speaks in place of an image. Here is how to write alt text that tells a listener what the picture is there to say, in a sentence or two.

To write alt text people can use, ask what a sighted reader takes away from the image, and put that meaning into plain words. Describe the point of the picture in its place on the page, and leave the rest. If the image adds nothing to the page, mark the image as decorative so the screen reader skips the image.

Good alt text is short, specific, and written for the page where the image appears. The same photo can need different words on two different pages.

What is alt text, and who hears the words?

Alt text lives in the code behind an image, in a part called the alt attribute. Screen readers such as VoiceOver, TalkBack, NVDA, JAWS, and Narrator read alt text out loud when they reach the image. The same words show up when an image fails to load, and search engines read them, too.

The accessibility standards ask for a text alternative for every image that carries meaning. In the Web Content Accessibility Guidelines (WCAG), this is success criterion 1.1.1, Non-text Content, at Level A, the most basic level.

Here is what a listener can hear when an image has no alt text at all:

"Image. I M G underscore 4 4 7 1 dot J P G."

Many screen readers fall back to reading the file name, because the page gives them nothing better. Here is the same image with alt text written for a page that sells rain jackets:

"Image. A woman in a yellow rain jacket with the hood up, zipped to the chin in heavy rain."

The listener now knows what the product looks like and what the photo is trying to show.

Here is how to write alt text in four steps.

1. Ask why the image is on the page. A photo can show a product, explain a step, set a mood, or prove that an event happened. The purpose decides what the words need to say.

2. Write what a sighted reader would take away. Put the most important detail first, since a listener may move on after a few words.

3. Leave out "image of" and "picture of" at the start. The screen reader already announces that the element is an image. Do name the kind of image when the kind matters, such as a screenshot, a logo, a painting, or a map.

4. Read the alt text out loud in the sentence around the image. If the words repeat the caption or the paragraph next to the image, cut them down. If a listener would still ask "what does that show?", add the missing detail.

Context changes the words. On a page about a city's flood warnings, the same rain photo might need this instead:

"A street under ankle-deep water after a storm, with a woman in a rain jacket wading across."

Neither description is wrong. Each one fits the reason the photo appears on its page.

Which images need a different kind of alt text?

A few kinds of images follow their own rules. These are the cases to check first.

• Decorative images get an empty alt attribute. A background texture or a divider line carries no meaning, so give the image an empty alt attribute, and the screen reader will skip the image. I would not leave the alt attribute off entirely, because some screen readers then read the file name.

• Linked images and icon buttons describe the action. When an image is a link or a button, the alt text says where the link goes or what the button does, such as "Search" or "Go to the home page."

• Images of text repeat the words. A graphic with words in the picture needs those same words in the alt text. Real text on the page is better still, because the reader can resize real text and a screen reader can read real text without help.

• Charts and diagrams need a short summary and the full data. Give a short alt text that names the chart and its main finding. Then put the full data in a table or a paragraph on the page, where everyone can reach the data.

• Logos use the organization's name. If the logo is also a link, say where the link goes.

• Photos of people describe what matters to the page. Focus on what the person is doing or showing. Avoid guessing at someone's race, gender, age, or disability unless the content depends on that detail and you know the detail is true.

Can AI write your alt text for you?

AI tools can describe what is in a picture, and a draft from one can save time on a large library of images. A tool can't know why you put the image on the page, though, and the tool will sometimes describe a detail wrong with full confidence.

I suggest treating an AI description as a first draft. A person who knows the page reads the draft, fixes what is wrong, and fits the words to the purpose of the image.

Where do you add alt text?

Most site builders, email tools, and social media apps have a place for alt text in an image's settings. Look for a field called "alt text," "image description," or "accessibility" near the image when you upload or edit the image. In code, the words go in the alt attribute of the image tag.

While you're checking your images, try one more test that takes only a few minutes. You can try your own website without a mouse and see where the keyboard gets stuck.

Why does good alt text matter for your business?

Blind and low vision customers decide whether to buy, book, or trust you partly from what your images tell them. When the alt text is missing, a product photo is a blank space and a chart is a mystery. Good alt text also helps anyone on a slow connection, and the words give search engines a clear sense of what each image shows.

The work is small, one image at a time. Once a team knows the questions to ask, writing alt text becomes part of adding an image to the page.

In short

• Alt text tells a listener what an image means on the page, so ask why the image is there before you write a word.

• Keep alt text short and specific, skip "image of," and give decorative images an empty alt attribute.

• AI can draft a description, and a person still checks the draft and fits the words to the page.

If you'd like me to review the images and the rest of your site, from a single flow to a whole product, explore my accessibility audits.