Missing Alt Text: What It Is and How to Fix It
Alt text is the short written description attached to an image so people who cannot see it still get the information. When it is missing, a screen reader has nothing to say about the image, or reads out the file name instead. Missing alt text is one of the most common accessibility failures on the web - we found it on 38 of the 299 large US home pages we scanned. WCAG Success Criterion 1.1.1 (Level A) requires a text alternative for every image that carries meaning; purely decorative images should have an empty alt so they are skipped. The hard part is not adding the attribute - it is writing alt text that is actually useful, which a scanner cannot check for you.
Most images on a page are doing a job. A product photo, a chart, a headshot in a bio, a logo that links home: each carries information or function that a sighted visitor takes in at a glance. Alt text is how that same information reaches someone using a screen reader, and how it survives when an image fails to load on a slow connection. This page covers what alt text is, the three kinds of images and how to handle each, who missing alt text shuts out, and how to fix it.
What alt text is and what WCAG requires
The alt attribute on an <img> is a text alternative that assistive technology reads in place of the image. WCAG Success Criterion 1.1.1 Non-text Content, at Level A, requires that all non-text content has a text alternative that serves the equivalent purpose - with one deliberate exception: an image that is purely decorative should be given an empty alt so it is ignored.
That splits images into three cases, and the right alt depends on which one you have:
| Image type | What it does | What the alt should be |
|---|---|---|
| Informative | Conveys content (a photo, a chart, a diagram) | A few words describing the content or its takeaway |
| Decorative | Visual only (a background flourish, a divider) | Empty: alt="" so it is skipped |
| Functional | Is a link or a button (a linked logo, an icon) | The destination or action, not the picture |
<!-- Informative: describe the content -->
<img src="growth.png" alt="Monthly signups doubled after the March redesign">
<!-- Decorative: empty alt so a screen reader skips it -->
<img src="divider.svg" alt="">
<!-- Functional: the alt is the link's purpose -->
<a href="/"><img src="logo.svg" alt="Acme Bank home"></a>
Who missing alt text shuts out
- Screen reader users, most directly. A meaningful image with no alt is either silence where information should be, or the screen reader falling back to reading a file name like "IMG_4032.jpg".
- People on slow or failed connections, who see the alt text in place of an image that did not load.
- Search engines, which read alt text to understand images - so good alt is also an SEO and a discoverability win, not only an accessibility one.
How common is it?
In our State of Web Accessibility 2026 study of 299 large US home pages, 38 (13%) had at least one image with no alt attribute. It was most common on nonprofit sites (10 of 43) and online retail sites (8 of 33) - the sites built around photography, donation appeals, and product imagery, where there are simply more images to miss. Text-heavy sectors had almost none; higher-education home pages had zero.
The number understates the real problem, in a way worth being honest about. A scanner counts images with no alt attribute. It cannot count the images that have an alt of "image", or "DSC_0019", or a marketing caption that does not describe the picture - all of which pass the automated check and still tell a screen reader user nothing. The true rate of unhelpful alt text is higher than 13%.
How to write alt text well
A few rules cover most cases:
- Be brief and accurate. A few words that capture what the image conveys in context. WebAIM's guidance puts it plainly: "Typically, only a few words are necessary."
- Do not write "image of" or "photo of". A screen reader already announces it as an image; the prefix is wasted.
- Match the context. The same photo of a running shoe might be
alt="Trail running shoe, side view"on a product page, oralt=""if it is decorative beside text that already describes it. - Charts and complex images get a summary plus detail. Put the takeaway in the alt ("Revenue grew 30% in 2026") and the full data in a nearby table or linked description.
- Decorative means empty, not missing.
alt=""is a deliberate signal to skip; a missing attribute is a gap.
How to fix it
- Find the images with no alt. Run a scan or use axe DevTools to list every
<img>missing analtattribute. - Sort each into informative, decorative, or functional. The bucket decides the alt.
- Write succinct alt for informative images - the content or takeaway, no "image of".
- Give decorative images
alt=""- empty, not absent. - Name functional images by action - a linked logo gets the company name, a search icon gets "Search".
- Summarize complex images in the alt and put the detail nearby, then re-scan and spot-check that what you wrote makes sense.
Skip the "overlay" widgets that promise to generate alt text automatically. Auto-generated descriptions are routinely wrong or generic, and the Federal Trade Commission fined the overlay vendor accessiBe one million dollars in 2025 over claims its tool could make any site conform. A human who knows what the image is for writes better alt in seconds. We cover why overlays fall short in detail.
What a scan can and cannot tell you
A scan is reliable on the missing-attribute half: it finds every image with no alt, because that is a fact about the markup. It cannot judge the writing - alt="image" passes the automated check and helps no one. That is the part a person has to do: read each alt and ask whether it conveys what the image conveys. We test the automated slice and say so; the human read of alt quality is part of a full audit.
Common questions
What is alt text? The alt attribute on an image - a short text alternative a screen reader reads, and that shows if the image fails to load.
What makes good alt text? Accurate and brief, a few words in context, no "image of"; charts get a summary plus detail nearby.
Should decorative images have alt text? They should have an empty alt="", so screen readers skip them - not a missing attribute.
Does missing alt text fail WCAG? A meaningful image with no alt fails 1.1.1 (Level A).
Check your own site
Run a free check on your home page to see every image missing an alt attribute, with the markup to fix, in about a minute. For the whole site, see what a full audit covers, and how monitoring catches the images that ship without alt every time a new page or banner goes up. For the data behind this page, read the State of Web Accessibility 2026; its companion failures are low color contrast and links without discernible text.