How to Write Alt Text That Is Actually Accessible
Alt text is not decoration for screen readers. It is how visually impaired users understand your images.
Alt Text Is Content, Not a Checkbox
Alt text is the short description read aloud by screen readers in place of an image. For a sighted user, it is invisible. For a blind or low-vision user, it is the entire image. Treating it as a formality to satisfy an audit means handing a quarter of your audience a blank page where a picture should be.
The most common mistake is writing alt text for the search engine instead of the reader. People stuff keywords into the attribute and call it accessible, when all they have done is make the screen reader drone through an irrelevant string of SEO terms. Accessibility and SEO can both win, but only when the text is written for the human first.
Good alt text answers one question: what does this image contribute to the page that the surrounding text does not already say? If the answer is nothing, the image is decorative. If the answer is something specific, the alt text has to capture that specific thing.
The Core Rules in Plain Terms
- Describe what the image shows, not what it symbolizes. A photo of a cracked phone screen is a cracked phone screen, not "the fragility of modern life."
- Keep it short. Around 125 characters is the practical limit before screen readers start cutting off the description.
- Skip "image of" and "picture of." The screen reader already announces that it is an image. Saying it again wastes the user's time.
- Do not repeat the caption. If the caption already says "The team in 2023," the alt text should add what the caption cannot show.
- Leave purely decorative images empty, with an empty alt attribute, so the screen reader skips them entirely.
Same Image, Three Different Alt Texts
| Approach | Alt text | Verdict |
|---|---|---|
| Keyword-stuffed | buy cheap running shoes sale discount athletic footwear | Fails the reader, borderline spam |
| Over-descriptive | A photograph of two brown leather running shoes on a gray concrete surface with laces tied | Too long, buries the point |
| Just right | A pair of brown leather running shoes | Clear, short, and accurate |
Decorative images, like a background swoosh or a divider line, should have an empty alt attribute, written as alt="". This tells the screen reader to skip them. Never delete the attribute entirely, because some readers will then read out the image filename, which is worse than no description at all.
A Process for Writing Alt Text Quickly
- 1Ask what the image is for
Before writing a word, decide the image's job. Is it conveying information, setting a mood, or just decorating the layout? The job determines whether you write full alt text, a short label, or leave it empty.
- 2Pretend you are describing it on a phone call
Imagine you are talking to someone who cannot see your screen, and you have one sentence to tell them what matters. Whatever you would say in that sentence is your alt text. This naturally keeps it short and focused on the essential detail.
- 3Check it against the surrounding text
Read the paragraph around the image. If the alt text just repeats information already on the page, cut it down or leave it empty. The goal is to add what is missing, not duplicate what is already there in words.
- 4Cut the filler words
Remove "image of," "photo of," and any adjectives that do not change the meaning. What remains should be a tight noun phrase that conveys the image's content without preamble or decoration.
Special Cases That Trip People Up
Charts and data visualizations are the hardest images to describe, because the information is the entire point. A short alt text like "Bar chart of sales by quarter" is a good summary, but you should also include the actual numbers in the surrounding text or a linked data table. The alt text labels the chart, the page provides the detail.
Images of text, like a screenshot of a tweet or a quote graphic, need the text transcribed into the alt attribute. A screen reader user cannot read text baked into an image, so the alt text has to carry the full message, word for word, exactly as it appears.
Logos are functional, not decorative. The alt text should name the company, such as "AI Humanizer Lab logo," so the user knows whose site they are on. This is one of the few cases where naming the brand in alt text is the correct and accessible choice.
Why This Matters in Numbers
If you replaced the image with your alt text and read the page aloud, would a blind reader get the same experience as a sighted one? That is the entire standard.
Alt Text and SEO Work Together
There is a persistent myth that accessible alt text and SEO are at odds. They are not, once you write for the reader. Search engines read alt text to understand images, and they reward descriptions that genuinely describe the picture. Keyword-stuffed alt text was a trick from a decade ago, and it now reads as spam to both algorithms and screen readers.
Write the description a person would want, and the search ranking follows. The two goals collapse into one the moment you stop trying to game either of them. Good alt text is the rare case where doing the right thing for users is also the right thing for traffic.
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