Alt Text Checker
Paste raw HTML and instantly see which images are missing alt text.
About the Alt Text Checker
Paste any HTML snippet or full page source and the checker runs it through the browser's built-in DOMParser to pull out every <img> tag, then flags the ones with a missing or empty alt attribute. Screen readers can't describe an image that doesn't describe itself, and search engines can't index what they can't read, so it's worth catching before a page goes live.
Empty alt text isn't always a mistake
Worth knowing before treating every flagged image the same way: alt="" is the correct, deliberate choice for a purely decorative image, a background flourish, a spacer, a repeated icon that adds nothing informational, it tells a screen reader to skip the image entirely rather than announce something meaningless. This checker flags both a missing alt attribute and an empty one as problems, since both look identical from the outside without inspecting the image itself, but the fix for each is different, a genuinely decorative image should keep alt="" on purpose, while a meaningful image just needs real descriptive text written in.
Missing entirely is worse than empty
An <img> tag with no alt attribute at all behaves differently from one with alt="", screen readers commonly fall back to announcing the image's filename or file path when the attribute is absent, which sounds like "IMG dash 4471 dot jay peg" read aloud rather than silence. That's a worse experience than either a real description or a deliberate empty string, which is part of why this checker treats a missing attribute and an empty one as the same category of issue, both need a decision made, just not necessarily the same fix.
What makes alt text actually useful, not just present
Alt text that just says "image" or repeats the surrounding heading verbatim technically satisfies the attribute's presence without adding real information for someone who can't see the image. A useful description states what the image actually shows or conveys, concisely, without needlessly prefixing it with "image of" or "picture of," a screen reader already announces that it's an image before reading the alt text, so that phrase is redundant. For a genuinely informational image, a chart or diagram, the meaningful content it conveys belongs in the alt text or the surrounding page copy, not left implicit in something only a sighted visitor can interpret.
What this checker doesn't catch
Only real <img> tags are checked here, a background image applied through CSS, background-image: url(...), doesn't appear in the parsed HTML at all and can't be flagged by a tool working from markup. Background images used purely for decoration are fine left as-is, but a background image carrying real informational content, uncommon but it happens, needs that information provided some other way on the page, since CSS background images have no alt-text equivalent for assistive technology to read.
Why this matters for search visibility, separately from accessibility
Google's image search relies heavily on alt text to understand what an image depicts, since it can't reliably interpret the visual content of most images the way a person can. A product photo, infographic, or diagram with no alt text is effectively invisible to image search, missing out on a source of traffic entirely separate from a page's regular text-based ranking. This is one of the rare cases in SEO where the same fix, writing genuinely descriptive alt text, directly serves two different audiences at once, screen reader users and image search crawlers, rather than being a trade-off between them.
A practical workflow for a page full of images
Paste a page's full HTML in here first to get the total count and the list of flagged images by source path, then work through that list rather than re-reading the entire page source by eye looking for missing attributes. For a page with dozens of images, most of them from a CMS or a component library, this catches the handful that actually need attention far faster than manually scanning rendered HTML for a specific attribute mixed in among everything else in the tag.
Frequently Asked Questions
Is an empty alt="" attribute always a mistake?
No. alt="" is the correct choice for purely decorative images, it tells screen readers to skip the image rather than announce something meaningless. This checker flags it alongside missing alt attributes since both look the same from the outside, but a decorative image should keep alt="" deliberately rather than gain a description it doesn't need.
What happens if I just leave off the alt attribute entirely?
Many screen readers fall back to announcing the image's filename when the alt attribute is missing entirely, which is often a worse experience than either a real description or a deliberate empty string. Every image should have an alt attribute, even if that attribute is intentionally set to empty.
Should alt text start with "image of" or "picture of"?
No, that phrasing is redundant. A screen reader already announces that an element is an image before reading its alt text, so leading with "image of" just adds extra words without adding information. Describe what the image actually shows instead.
Does this tool check background images set with CSS?
No. Only real img tags in the parsed HTML are checked. A CSS background-image has no alt-text equivalent and won't appear in this checker's results, purely decorative background images don't need one, but a background image carrying real information needs that information conveyed some other way on the page.
Does alt text actually affect SEO, or is it just for accessibility?
Both. Google's image search relies heavily on alt text to understand what an image shows, since it can't reliably interpret visual content the way a person can. An image with no alt text is effectively invisible to image search, so writing genuinely descriptive alt text serves accessibility and image search visibility at the same time.