How to find missing alt text on a website

Quick check in the browser console

Open the page, press F12 (or Cmd+Option+I on a Mac) to open developer tools, and run this in the Console:

document.querySelectorAll('img:not([alt])')

It lists every <img> with no alt attribute. Images with alt="" are not listed, because an empty alt is correct for decorative images — check those by eye.

Check any page with the AltVision extension

1. Install AltVision from the Chrome Web Store or Firefox Add-ons.
2. Open the page you want to check and click the AltVision button in the toolbar.
3. Turn on Enable alt text tooltips. Each image shows its alt text; images without it show No alt text – click to generate.
4. Click a flagged image to generate a suggestion from the image and the text next to it, then copy it into your CMS. Generating needs a premium licence, credits, or your own OpenAI or Claude API key; the checks themselves are free.

The extension only changes what you see in your own browser; the site itself is untouched. Nothing is sent anywhere until you click to generate alt text for an image.

The Batch Alt Text Manager lists the images on the page so you can select them, generate alt text together, and review the results side by side. The free version shows the first five images; premium shows them all.

Check the rest while you're there

Missing alt text rarely comes alone. The same extension includes tools for the other common checks:

• Show ARIA attributes to see the labels screen readers announce for buttons and links.
• Highlight Headers to check that the heading structure makes sense.
• Focus Finder and Tab order to follow keyboard navigation through the page.
• Vision Simulator to preview the page with protanopia, deuteranopia, tritanopia, achromatopsia, blurred or low vision.
• Contrast Ratio Checker with an eyedropper, rated against WCAG AA and AAA for normal and large text.

Fixing it at the source

If the site runs on WordPress, fix alt text where it's stored instead of page by page — see how to add alt text in WordPress. For what each image should say, see how to write good alt text.

Questions

How do I find images without alt text?

Run document.querySelectorAll('img:not([alt])') in the browser console, or install the AltVision extension and turn on alt text tooltips, which flag every image that has none.

Is an empty alt attribute the same as missing alt text?

No. alt="" deliberately marks an image as decorative so screen readers skip it. A missing alt attribute is an error, and screen readers may read the file name instead.

Is the AltVision extension free?

Yes, the checking tools — alt text tooltips, ARIA attributes, headings, focus and tab order, vision simulator and contrast checker — are free. Generating alt text uses a premium licence, prepaid credits, or your own OpenAI or Claude API key.