Alt Text Checker
Alt text is the HTML attribute that describes an image in words. For someone using a screen reader it is the image, and for a search engine it is the strongest signal about what the image shows. This tool scans every image on the page you enter and audits the alt text not just for presence but for quality: links with no accessible name, alt text that is nothing but a filename, duplicate descriptions, lengths a screen reader will cut off and suspected keyword stuffing are each reported separately.
What is alt text for?
Alt text has two jobs, and one sentence can do both. The first is accessibility: a blind reader listening to the page with a screen reader hears this text in place of the image. The second is search: Google uses the alt attribute, along with the surrounding text, to work out what the image shows, and image-search matching is largely built on it. It's also the text a browser displays in the box when an image fails to load. What all three have in common is this: alt text should describe the image to someone who cannot see it.
For decorative images, alt="" is the correct usage
Not every image needs describing. Dividers, corner patterns and background textures carry no meaning; they are decorative, and the right move there is not to delete the alt attribute but to leave it empty: alt="". An empty alt tells the screen reader to skip the image, so the user isn't interrupted for nothing. A missing attribute is a different situation: some screen readers fill the gap by reading the filename, and the user hears something like "i-m-g dash 2 4 5 1 dot j-p-g". This tool distinguishes the two cases and never counts your alt="" usage as an error.
Images inside links: the most commonly missed mistake
When an image sits alone inside a link and the link has no text of its own, that link's accessible name depends entirely on the alt text. If the alt text is missing too, a screen reader has nothing to announce; a user tabbing through hears only "link" and has no idea where it goes. WCAG success criterion 2.4.4 addresses exactly this. Logo headers, social media icons and image banners are where this mistake shows up most. This tool tells the cases apart by checking whether the link has its own text: an empty alt on a decorative image inside a text link is fine, while the same thing inside a textless link is a serious defect.
Length: why is 125 characters the benchmark?
HTML sets no length limit on alt text, but common screen readers tend to cut off around 125 characters. That's why the accepted industry benchmark is to keep alt text under 125; in practice a sentence of 5 to 15 words covers most images. If an image genuinely needs a long description, a complex chart for instance, the right approach is to keep the alt text short and move the detail into the page text or a <figcaption>. That way the screen reader user and the sighted reader get the same information.
Why keyword stuffing backfires
Turning the alt attribute into a keyword list is an old habit with no payoff today. Google's image guidelines are explicit: stuffing alt text with keywords creates a poor user experience and can get a site judged as spam. Here's the test: read the alt text aloud, and if you hear a natural sentence describing the image, it's written correctly; if you hear comma-separated terms, that's a search query, not a description. Having the keyword appear in the alt text is fine, as long as it's a natural part of the sentence.
Duplicate alt texts
When different images on a page carry the same alt text, it usually means a template is filling it in automatically, such as writing the shop name onto every image in a product list. That misleads screen reader users, since images that differ sound identical, and it gives the search engine nothing distinguishing to work with. Every image should describe its own content; the product name is the right starting point in a listing, and the scene itself in a gallery.
Your Questions
Frequently Asked Questions
Does alt text directly affect SEO?
In image search, yes, directly: Google works out what an image shows largely from its alt text and the text around it. Its effect on the page's overall ranking is indirect; alt text is one of the signals supporting the page's topic, not a ranking factor on its own. Writing alt text as a description of the image rather than as a ranking device produces the right result in both places.
How long should alt text be?
Under 125 characters is the safe benchmark, because common screen readers may cut off around there. In practice a sentence of 5 to 15 words covers most images. There's no lower limit, but one-word labels rarely describe an image adequately.
Can I just delete the alt attribute on a decorative image?
No, the two aren't the same. Use alt="" on decorative images; that tells the screen reader to skip them. Deleting the attribute entirely creates ambiguity, and some screen readers fill the gap by reading out the filename.
What's the difference between alt text and the title attribute?
Alt text is the image's text equivalent, standing in for it when the image can't be displayed or is being listened to with a screen reader. Title is the tooltip that appears on hover; it's invisible on touch devices and screen reader support for it is inconsistent. Putting the same text in both makes some readers announce the same information twice. Title is usually unnecessary; don't use it unless it carries different information.
My images have alt text, so why is the tool still warning me?
This tool looks at what the alt text says, not just whether it exists. Alt text that is only a filename, the same text repeated across several images, lengths over 125 characters, redundant prefixes like "image of", and comma-separated keyword lists are each reported separately. An alt attribute that is filled in but doesn't describe the image produces much the same result in practice as an empty one.
How do I give alt text to images loaded as backgrounds?
Images loaded as CSS backgrounds have no alt attribute; screen readers never see them at all. For decorative images that's not a problem, and is in fact an appropriate technique. But serving an informative image as a background is an accessibility mistake; that image should be delivered with an <img> tag and its own alt text.
Does this tool crawl my whole site?
No, it audits the single page you enter. To check the images across every page of your site at once, use our Deep Crawl tool; it walks the whole site and applies these same rules to every page.