Images missing alt text: how to find and fix them

One or more images on the page have no alt attribute at all. Give meaningful images a short description of what they show, and give decorative ones an empty alt="" so screen readers skip them. Fix it in the image component, so a missing alt cannot ship again.

Updated 28 September 2026

Severity
Warning
Issue type
images-missing-alt
How the audit flags it
An HTML page returning 2xx is flagged when at least one <img> element has no alt attribute. An empty alt="" is correct markup for a decorative image and is never flagged. CSS background images and inline SVG are not <img> elements and are not checked. The issue records how many images lack alt out of the total.
How to check
One URL at a time in the free SEO checker, or every page in a site audit.

Why alt text matters

Alt text is what a screen reader announces in place of an image, and what a browser shows when the image fails to load. Without it, many screen readers read out the file name instead, so a visitor hears IMG underscore 4471 dot jpg.

Search engines use it too. Google uses alt text, along with the page content around it, to understand what an image shows. For image search, and for pages where an image carries meaning a caption does not, it is the main text signal an image has.

It is also an accessibility requirement under WCAG, which matters for public sector sites and for anyone selling to them.

Missing is not the same as empty

<img src="divider.png"> has no alt attribute. The screen reader has no instruction, so it guesses, usually by announcing the file name.

<img src="divider.png" alt=""> has an empty one. That is an explicit instruction: this image is decorative, skip it. It is the right markup for dividers, background flourishes and icons that sit next to a text label.

That is why the audit flags only images with no attribute. Adding alt="" everywhere would silence it, and would also hide every meaningful image from screen reader users. Decide per image.

What to write, and where to fix it

The W3C's alt decision tree covers the edge cases. The short version:

  • A photo or illustration that adds information: describe what it shows, in the context of the page, in a sentence or less. No "image of".
  • A linked image or an icon button with no text: describe what the link or button does, not what the icon looks like.
  • A chart or diagram: summarise the takeaway in the alt, and give the detail in the surrounding text.
  • Decorative, or already described by adjacent text: alt="".

Then fix the component. If the site renders images through one Image component, make alt a required prop, so the build fails when it is left out. In a CMS, make the alt field required on upload, and treat the file name as something that never reaches the page.

The free SEO checker reports how many images on one URL lack alt text, which is enough to confirm a component fix.

Fix it with a coding agent

Connect Claude Code, Cursor or Codex to IndexZero's MCP server, open your site's repo, and paste:

Run a site audit of example.com and wait until it completes. Read the images-missing-alt issues and, for the affected pages, find the components in this repo that render images without an alt attribute. Make alt a required prop on the shared image component. For each existing image, write alt text describing what it shows in the context of its page, or use an empty alt if it is purely decorative, and list which you chose for each. Show me the diff before committing.

Behind that prompt the agent calls run_site_audit, polls get_audit_status until the crawl completes, and reads get_audit_issues with issueType: "images-missing-alt". Your repo is where the fix happens: IndexZero reads your site and never changes it.

Frequently asked questions

Is missing alt text an SEO problem or an accessibility problem?
Both, but mostly accessibility. The SEO effect is largest for image search and for images that carry information the page text does not repeat.
Should I put keywords in alt text?
Only when they describe the image. Alt text is read aloud to people. Google's image guidance warns against filling alt attributes with keywords.

Audit the whole site

Find every page with this issue

An agent connected to IndexZero's MCP server can crawl the whole site, read the issues of one type, find the templates in your repo and fix them, then re-crawl to confirm. The crawl itself spends no credits; only the optional Lighthouse sample does. The free plan includes the MCP server, audits of up to 50 pages, and 2,000 credits a month.

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