Image Alt Text Checker

It fetches one page, up to 900 KB, and reads every <img> element in the HTML the server sends. For each image it notes the alt attribute (absent, empty or its text), the image address, any aria-hidden or role attribute, whether an element around it has aria-hidden="true", the width and height, and whether the image sits inside a link.

It reads up to 300 images. Past that, the report says how many more images on the page were not checked. A page that returns an error status or is not HTML stops the check: “The page returned HTTP 404, so there are no images to check.”

For the image address it prefers data-src and data-lazy-src over src, because lazy-loading plugins put a placeholder in src and the real file in one of those. That is the address shown in the Image column.

Each image gets exactly one status. The checker tests them in this order and stops at the first that matches, so an image hidden with aria-hidden, on the image or on an element around it, is reported as decorative even if it has no alt attribute.

The headline counts the images in Images to fix. It reads “N images to fix” when at least one has no alt attribute or is a linked image with empty alt, the two cases that break things for screen reader users. It reads “N images could use better alt text” when the only problems are file names, filler words or an “image of” opening. “No images need fixing” means none of those were found.

Images to fix lists the problems worst first, with the image address, its current alt and the reason. Empty alt: check these are decorative lists every unlinked image with alt="". Those are not errors. Empty alt is the right answer for a decorative image, and only you can tell which ones are. Images with descriptive alt, decorative images and tracking pixels are counted but not listed.

When the page looks like WordPress, a note under the lists says where to change alt text. For an image placed in post content, that is the image block, because changing the Media Library does not update images already placed. Featured images, the site logo and WooCommerce product images read the Media Library each time the page is built, so the note says to change those there. The section on where alt text lives covers the rest.

The W3C’s images tutorial, part of its Web Accessibility Initiative, sorts images by the job they do, and the job decides the alt text. WCAG 1.1.1, Non-text Content, a Level A requirement, asks for a text alternative that serves the same purpose as the image. For a purely decorative image, that purpose is nothing, so the alternative is an empty alt.

A quick test from the same tutorial: if you removed the image, would a visitor lose information? If not, it is decorative. If the image is next to text that says the same thing, an empty alt avoids reading it twice.

Describe what the image shows in the context of the page. The same photo of a loaf needs different alt text in a post about crumb structure and in a post about scoring patterns. Leave out “image of” and “picture of”: screen readers already announce that it is an image.

Google’s image guidance says it uses alt text together with computer vision and the page’s content to understand an image, and asks for useful, information-rich alt text that uses keywords appropriately, not a list of keywords. Its own example improves “puppy” to “Dalmatian puppy playing fetch”. Google also uses the alt text of a linked image as that link’s anchor text.

There is no fixed length limit in the HTML standard or in Google’s guidance. Write what the image adds, which is usually one short sentence or less. Save long explanations for the caption or the body text, where every visitor can read them.

WordPress keeps alt text in two places. Each item in the Media Library has an Alternative Text field. And each image placed in a post’s content carries its own copy of the alt text in the post’s HTML. When you insert an image, the editor copies the library’s alt into the post. After that the two are separate: editing one does not change the other.

Which copy a visitor gets depends on how the image is placed, which is why fixing an image in the Media Library sometimes works and sometimes changes nothing.

Themes that unlink the logo on the home page also set its alt to empty there, because the site title sits next to it. The checker lists it under Empty alt to review, and on that page it is correct.

Some SEO plugins fill in alt text automatically. That can explain alt text you never wrote, and why the checker flags it.

Rank Math has Add missing ALT attributes under Rank Math SEO → General Settings → Images, a tab that appears once its Image SEO module is on. It is off by default, and its default format is %filename%. When it is on, Rank Math fills the alt of images in post content, featured images and WooCommerce product images as the page is built, using the file name with hyphens and underscores turned into spaces and the size suffix removed. Nothing is saved to the Media Library. Two side effects show up in this checker: IMG_4521.jpg becomes “IMG 4521”, which is flagged as a file name, and images you left empty on purpose get the file name too, because the setting fills empty alt as well as missing alt.

SEOPress can set alt text from the file name when you upload an image, under SEO → Advanced → Image SEO (as of October 2026). Unlike Rank Math’s, that alt is saved to the Media Library, so it reaches new posts too, and a camera file name becomes a camera alt.

Yoast SEO does not write alt text. Its content analysis checks whether a post has images and whether their alt text includes the focus keyphrase. Treat that as a reminder, not a target: work the keyphrase in only where it describes the image.

Illustrative values. A food blogger checks a sourdough recipe post on a site running Rank Math with Add missing ALT attributes on. The page has 14 images.

After the edits, the re-run reads 11 descriptive, 1 empty to review (the divider) and 2 decorative, with the verdict No images need fixing. The owner also renamed new uploads before adding them, so the plugin’s fallback has something better to work with.

When the report does not match what you expect, the cause is usually the difference between the HTML the server sends and the page you see in a browser.

Re-run the checker on the same URL after clearing the page cache. To hear what a screen reader gets, open the page in Chrome, inspect the image, and read its computed Name in the Accessibility pane of DevTools.

In Search Console, Performance with the search type set to Image shows clicks and impressions from Google Images. Alt text is one input among several, so treat a change there as a trend over weeks, not proof of one edit.

Leave these alone: decorative images with empty alt, tracking pixels, the home-page logo next to the site title, and images marked aria-hidden on purpose. And there is no need to chase a perfect score on templates you cannot edit: fix the images in your own content first, where most of the meaning is.

Fixing alt text one image block at a time across an old blog is slow. RankHive drafts alt text for images in your posts and pages, and you approve it before its plugin writes it to WordPress.