Alt text describes what information or function an image conveys on a page. It helps people who use screen readers or cannot see the image, and also gives search engines additional context. Good alt text is written for a specific image in a specific place on the page. Filling this field with keywords or a filename is not enough.
What the error data shows
In its 2026 WebAIM Million report, automated testing found missing alternative text as an error on 53.1% of homepages in a sample of one million websites. This figure represents the share of pages with this error, not the share of all images on the internet. WebAIM separately reports that 16.2% of images on the tested homepages had no alt text; empty `alt=""`, which is used for decorative images, was not included in this figure. Among images without alt text, 45% were links. WebAIM Million 2026 report.
The report also notes that 10.8% of images with text had text that seemed questionable or repetitive: for example, it called the image “image,” repeated the filename, or duplicated nearby text. WebAIM analyzed homepages and used the automated WAVE tool on the rendered DOM. This is a useful overview of common issues, but it is not a manual check of every page or a complete assessment of a website’s accessibility.
The WHO estimates that 1.3 billion people, or about 16% of the world’s population, have significant disabilities. This figure covers all types of disabilities, not just people with visual impairments or screen reader users. For web images, the practical takeaway is more important: alternative text helps people who cannot perceive an image visually when it conveys information they need. WHO data on disability and health.
First, identify the image’s role
Before writing alt text, ask yourself: what should a person learn or do thanks to this image? The same file can play different roles on different pages. In a product gallery, differences between variants matter; in an article about design, the composition or a detail may matter; in a linked logo, where the link leads matters.
| Image type | What to convey | Example |
|---|---|---|
| Informative photo or illustration | The main detail that matters to the page’s topic | “An engineer measures the diameter of a metal part with calipers” |
| Decorative background or divider | Nothing, if removing the image does not change the page’s meaning | Empty `alt=""` attribute |
| Icon button or linked image | The action or purpose of the link | “Search the site” or “Open catalog” |
| Chart or complex diagram | A brief takeaway; provide details in text or a nearby table | “Sales increased in the third quarter; monthly data is shown below” |
For a purely decorative image, set the value to empty: `alt=""`. A missing attribute and an empty attribute are not the same: an empty attribute tells assistive technology that the image can be skipped. If an image is the only content of a link or button, state the link’s purpose or the action in the alt text. For example, “Search” works for a magnifying glass icon, not “Magnifying glass.” If the adjacent text already says “Open catalog” and the icon adds nothing, its alt text can be empty so the screen reader does not read the same thing twice. This is in line with W3C WAI guidance on choosing alt text.
Write briefly, accurately, and in context
For an ordinary photo, a short phrase with the main content is often enough. “A ginger corgi carries a blue ball across the grass” says more than “dog” without listing every little detail in the frame. For a product card, name visible features that help distinguish variants, such as “black leather bag with short handles, front view.” Do not add characteristics that cannot be confirmed from the image.
Do not start descriptions with boilerplate such as “image 1,” “product photo,” or the filename. Screen readers usually announce that they have encountered an image. Words such as “photograph,” “icon,” or “illustration” are only needed when the image type is important for understanding its content.
There is no universally required 125-character limit for alt text. For a simple image, the description should be as brief as the meaning allows. A single phrase is often not enough for a chart or diagram: state the main takeaway in the alt text, then present the values, labels, and relationships in accessible text, a list, or a table nearby. This approach is recommended by W3C for complex images.
Alt text helps with search, but does not replace page text
Google uses alt text together with computer vision and page content to understand an image. For a linked image, alt text can also serve as the link text. So the description should match the image itself and the topic of the surrounding content, not be a separate list of keywords. Google warns that stuffing alt text with keywords worsens the user experience and may be considered spam. This does not mean that every poorly worded description automatically incurs a penalty. Google’s image SEO guidelines.
Do not claim that alt text universally “makes a page visible to AI.” It is useful for image search and understanding context, but Google considers both the image itself and the page text. The main goal remains the same: convey the information or function the user needs.
How to check alt text on your website
Start by crawling pages and templates: the homepage, categories, product pages, articles, case studies, and forms. Make a list of images missing an alt attribute, images with an empty value, repeated descriptions, filenames, and overly long lists of keywords. Do not automatically fix empty values: first make sure the images are truly decorative or duplicate nearby text.
For links and buttons, check whether their purpose can be understood without seeing the image. For informative images, assess whether the text helps convey the key meaning. An automated scanner can find empty fields and suspicious patterns, but it does not know what matters on a specific page. So check a sample manually, then test it with a screen reader or ask an assistive technology user to check the main scenarios.
When processing images at scale, AI can suggest draft descriptions, but they need to be checked against the page context and the images themselves. A model may mistake the object, color, number of details, or purpose of a link. Do not publish hundreds of automatically generated alt texts without checking them; otherwise, neatly filled-in fields will only create the appearance of quality.
The practical process is simple: identify the image’s role, choose the relevant details, write briefly, and check that the description does not repeat nearby text. Leave `alt=""` for decorative images, name the action for buttons, and add a full text explanation for complex infographics. This makes alt text useful both for accessibility and for helping search engines understand the page.
