Alt text describes an image to people who cannot see it and to search engines that cannot interpret it. Missing, over-long, or filename-shaped alt text is a small fix with a real payoff in accessibility and image search. Here is how to get it right.
The alt attribute is a short text description on an image. Screen readers read it aloud, browsers show it when an image fails to load, and search engines use it to understand what the image depicts. It serves accessibility and SEO at the same time.
A search engine cannot look at a photo and know what it shows the way a person can. It leans on the surrounding text and, heavily, on the alt attribute. Good alt text is how an image becomes eligible to rank in image search and how it adds relevant context to the page it sits on. But the larger reason to write it is accessibility: for a visually impaired visitor using a screen reader, the alt text is the image. A missing one is a blank where information should be.
The three findings in an audit map to the three common failures: no alt attribute at all, alt text so long it stops being a description, and alt text that is just the raw filename. The contrast below shows the difference:
Each check the audit runs on images.
The image has no alt at all, so screen readers announce nothing useful and search engines get no description. Fix by adding a concise alt describing what the image shows. The one exception is purely decorative images (borders, spacers), which should carry an empty alt="" so screen readers skip them.
Alt over roughly 125 characters stops being a quick description and becomes a paragraph a screen reader has to read out in full. Fix by tightening it to the essential subject. If the image genuinely needs a long explanation, put that in the surrounding text or a caption, not the alt.
Values like DSC_0042.jpg or hero-image-final-v2 describe nothing. This usually happens when a CMS auto-fills alt from the filename on upload. Fix by replacing each with a real description of the image's content.
Describe the image, in context, in a sentence.
Good alt text answers one question: if this image did not load, what would the reader need to know? Describe the subject and anything meaningful about it, in plain language, as if telling someone on the phone. "Red hiking boot on a rocky trail" beats both "boot" and "high-quality durable red waterproof hiking boot for mountain trails". Aim for a short, specific sentence, and let the natural description carry any keywords rather than forcing them.
Do not start with "image of" or "picture of", a screen reader already announces that it is an image. Do not stuff keywords; alt text overloaded with search terms reads badly to a screen-reader user and is exactly the pattern search engines discount. And for images that carry no information, decorative flourishes and spacers, use an empty alt="" so assistive technology passes over them instead of announcing a distracting filename.
For most pages the direct ranking effect is modest: alt text helps an image rank in Google Images and adds a little topical context to the page, but it will not move a competitive keyword on its own. Its weight grows for sites where images are the product, recipe photos, an e-commerce catalogue, a stock library, where image search is a real traffic source.
The accessibility case is stronger and unconditional. Every image that carries meaning needs alt text so that a visitor using a screen reader gets the same information as everyone else. Treating it as an accessibility requirement first, and an SEO bonus second, gets you both.
These are two separate signals. The alt attribute describes the image to people and engines; the filename is a smaller, secondary hint. A descriptive filename like latte-art.jpg is a minor plus over IMG_4821.jpg, but it never substitutes for real alt text.
The audit flags the filename-as-alt case specifically because it is the sign of an automated upload that filled both fields with the same useless string. Fixing the alt is the priority; renaming files is a nice-to-have you can do going forward rather than retrofitting across an entire library.
On a large site, missing alt is rarely one image; it is a pattern from a template or a bulk import. The fastest wins come from finding the source: a product template that never outputs alt, a gallery component that drops it, an importer that copied filenames. Fix the template and hundreds of images gain alt at once.
For the long tail of one-off images, prioritize the ones that matter: hero images, product photos, anything a visitor would ask about. A decorative background does not need a hand-written description; a page's main illustration does. An audit that lists every affected image by page turns a vague "add alt text everywhere" into a finite, sortable task.
Free to start. The audit lists images with missing, over-long, or filename alt, per page.
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