Image descriptions are one of the most misunderstood parts of on-page optimisation. Every SEO checklist tells you to fill in alt text, yet few explain what search engines do with it, how it differs from a caption or a description field in your media library, and why stuffing keywords into it can hurt more than leaving it blank. If you manage a content-heavy site, an online store, or a portfolio, the difference between describing images properly and describing them mechanically shows up in image search traffic, accessibility, and topical relevance.

The short answer is yes, image descriptions help, but only the ones search engines can actually read and only when they genuinely describe the image. Understanding which fields matter is the first step to using them well.

How AAMAX.CO Improves Image Optimisation at Scale

We are AAMAX.CO, a full service digital marketing company providing Web Development, Digital Marketing and SEO services worldwide. Image optimisation is one of those tasks that looks trivial on a single page and becomes a serious project across thousands of URLs, which is exactly where we help. We audit alt coverage, rewrite descriptions that add no value, fix filenames and delivery formats, implement image sitemaps and structured data, and build editorial guidelines so your team keeps it right going forward. Hire AAMAX.CO (https://aamax.co) if your visual content is not pulling the search traffic it should, and we will handle both the strategy and the implementation.

The Four Places You Can Describe an Image

Alt text is the attribute inside the image tag intended for people who cannot see the image. It is the single most important description for search because it is machine-readable, semantically defined, and used by assistive technology. Search engines use it to understand image subject matter and, in some cases, as anchor text when the image is a link.

Captions are visible text placed near the image, usually inside a figure element with figcaption. They are read by users and crawled as page content, which makes them useful for adding context that alt text should not carry. Titles are the optional title attribute that produces a tooltip on hover; they have minimal search value and are inconsistently exposed to users. Media library descriptions in systems like WordPress are stored in the database and often never rendered on the page at all, which means they typically contribute nothing to search unless your theme outputs them.

The fourth and often strongest description is the surrounding copy. The paragraph, heading, and section an image sits within tell search engines a great deal about what the image represents. An image placed inside a well-written section about industrial roofing membranes inherits that context whether or not the alt text is perfect.

Writing Alt Text That Actually Works

Good alt text describes what is in the image in plain language, as if you were telling someone on the phone. Aim for roughly five to fifteen words. Lead with the subject, add distinguishing detail, and include a relevant keyword only when it naturally belongs. Compare a weak example such as image1 or seo services company best seo agency with a strong one such as technician installing a rooftop solar inverter on a commercial building. The second tells a search engine and a screen reader user exactly what they are dealing with.

Skip phrases like image of or picture of because the element already declares itself as an image. Do not repeat the page title in every alt attribute across the page. For product photos, describe the variant, angle, and material rather than restating the product name ten times. For infographics and charts, summarise the key finding in the alt text and put the full data in adjacent text or a table so the information is not locked in a picture.

Decorative Images Should Have Empty Alt Text

Not every image needs a description. Spacers, background flourishes, decorative dividers, and icons that sit beside a text label carry no information. For these, use an empty alt attribute, written as alt equals two quotation marks with nothing between them. That tells assistive technology to skip the element instead of announcing a meaningless filename. Omitting the attribute entirely is worse, because screen readers may then read out the file path. Deliberate empty alt text is a sign of a properly built page, not a missing task.

Filenames, Formats, and Delivery Still Matter

Descriptions work best alongside sound technical hygiene. Name files descriptively before upload, using lowercase words separated by hyphens, so that a file reads as rooftop-solar-inverter-installation rather than a camera-generated string of digits. Serve modern formats such as WebP or AVIF, provide multiple sizes through srcset and sizes so mobile devices do not download desktop-scale files, and set explicit width and height to prevent layout shift.

Use native lazy loading for below-the-fold images but never for your largest visible image, since that directly harms Largest Contentful Paint. Make sure images are output as real HTML elements with a resolvable source, because an image injected only by script or set as a CSS background may never be indexed regardless of how well you describe it.

Structured Data and Image Sitemaps

For sites where images are commercially important, go beyond alt text. Add ImageObject markup with caption, licence, and creator information where appropriate, and include product, recipe, or article structured data on the containing page so search engines can associate images with rich results. Submit an image sitemap listing important files, which is particularly valuable for galleries, large catalogues, and pages using pagination or dynamic loading.

These signals also feed the systems that summarise and recommend content in AI-driven results. Clear descriptions and clean markup make it far more likely that an answer engine represents your visual content accurately, which is why image work forms part of both traditional optimisation and GEO services.

Mistakes That Cause Real Damage

Keyword stuffing in alt attributes is the most common failure. Repeating a target phrase across dozens of images on a page looks manipulative and does nothing useful for a screen reader user. Hiding text in alt attributes to game rankings is a clear violation. Copying the same description onto every image in a gallery removes any chance of differentiating them in image search. Leaving product images with default filenames from a supplier feed wastes an easy signal across an entire catalogue.

Accessibility failures carry legal exposure in many jurisdictions as well. Treating alt text as an SEO field rather than an accessibility feature is what leads to both problems at once.

Measuring the Impact

Track image performance separately. In Google Search Console, switch the Performance report search type to Image to see impressions and clicks earned by your files. Compare before and after a batch of alt text and filename improvements across a defined set of pages. Watch which images appear in rich results, monitor referral traffic from image search in analytics, and check Core Web Vitals to confirm your optimisation work has not slowed pages down.

The Bottom Line

Image descriptions help SEO when they are honest, specific, and rendered where search engines can read them. Alt text and captions do the heavy lifting, surrounding copy reinforces context, title attributes and unrendered media library fields do almost nothing, and decorative images should be explicitly skipped. Combine good descriptions with descriptive filenames, modern formats, structured data, and an image sitemap, and your visual content becomes a genuine traffic channel rather than decoration.

If you want this handled properly across a large site, our digital marketing and development teams work together to fix image optimisation at the template level so improvements apply everywhere at once. Reach out and we will start with an audit of what your images are currently earning.