Alt text

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Alt text is the short written description attached to an image on a web page. It lives in the image's code, not in the visible caption underneath it, and its job is to say in words what the picture shows. Search engines cannot look at a photograph the way a person does, so they read this text to understand the image. Screen readers do the same thing for visitors who cannot see the picture: they read the description aloud, so the reader gets the information the image was meant to carry.

Think of alt text as a plain-language label for one specific image. A good one answers a simple question: if this picture disappeared from the page and only the words remained, would the reader still understand what was there? If the answer is yes, the alt text has done its job. If the answer is no, or if the text only repeats the page headline, there is still work to do.

What alt text is, and what it is not

Alt text is a description, not a sales pitch and not a second headline. It describes the content of the image itself: the subject, the setting, and any action or detail that matters to the point the page is making. A photo of a baker kneading dough in a small kitchen, for example, is described as exactly that, in ordinary words, rather than as a string of search phrases.

It is not a caption. A caption is visible text that sits next to an image and adds context, commentary, or credit. Alt text is hidden from sighted readers and only appears when the image fails to load or when assistive technology reads it. The two can complement each other, but one does not replace the other. A page can have both, and often should.

Alt text is also not a keyword field. Stuffing it with repeated search phrases does not help readers, and it reads badly when a screen reader speaks it aloud. Search engines have long been able to tell the difference between a natural description and a list of phrases forced into a small space. The honest test is a spoken one: if the text sounds strange read aloud, it is probably written for a machine rather than a person.

Finally, alt text is not the same thing as a file name, although the two work together. A file name like a descriptive, hyphenated name helps organise images and gives search engines one more small clue, but it is the alt text that carries the full description. Good practice is to write both well, in plain words, and to keep them consistent with the topic of the page. The guide on image SEO for blog posts walks through naming and description side by side.

How alt text works

When a browser loads a page, each image carries an attribute in the page code where the description sits. If the image loads normally, sighted visitors never see that text. If the image fails to load, because of a slow connection or a broken file, the browser shows the alt text in the image's place, so the reader still knows what should have been there. That fallback alone makes alt text worth writing, even before search or accessibility enters the picture.

Screen readers handle it in a similar way. When the reader reaches an image, the software announces the description, letting a blind or low-vision visitor follow the same flow of information as everyone else. Without it, the software may announce only the file name, or skip the image entirely, leaving a gap in the article. For an image that carries real information, such as a chart, a diagram, or a before-and-after comparison, that gap can break the argument of the whole section.

Search engines use alt text as one signal among many when they try to understand a page. An image of a product, a process, or a place, described accurately, helps the engine connect the page with the topic it covers. It can also help an image appear in image search results, which is a separate way for readers to discover a post. Alt text is not the main driver of how a page performs, and no single description will lift a weak article, but a page where every image is described accurately is simply easier for both machines and people to understand.

There is one important exception to the write-it-always rule. Images that are purely decorative, such as a background flourish or a divider that adds no information, should carry empty alt text. That tells a screen reader to skip the image rather than interrupting the reader with a description of something meaningless. The skill is in telling the two kinds apart: if removing the image would remove information, describe it; if removing it would change nothing, leave the description empty.

Why alt text matters for a blog post and for search

For a blog post, alt text matters first for readers. Blog posts lean heavily on images: photos that set a scene, screenshots that show a step, diagrams that explain an idea. A reader using a screen reader deserves the same content as everyone else, and a reader on a slow connection deserves to know what failed to load. Writing alt text is a basic courtesy that also happens to be good craft.

For search, the honest scope is modest. Alt text helps search engines understand what a page is about, and it supports image search discovery, but it is one small part of on-page SEO. It works alongside the page's title tag, its meta description, its headings, and its body text. A post with excellent alt text and thin, unhelpful writing will not perform well, and a post with strong writing and missing alt text is leaving a real gap. The two sides belong together.

There is also a practical business reason. Small-business blogs are often read by customers who are deciding whether to trust a business. A site that works well for every visitor, including visitors using assistive technology, signals care and competence. That impression is hard to measure directly, but it is the same impression that makes someone stay on a page, read to the end, and get in touch.

Common mistakes

The most common mistake is leaving alt text blank on images that carry meaning. This usually happens not from laziness but from workflow: images are uploaded in a hurry, the description field is optional in most editors, and nobody notices until much later. Making the description part of the publishing checklist fixes most of it.

The second mistake is the opposite: writing the same generic text for every image, such as the business name or the article title repeated ten times. A screen reader then repeats the same phrase at every picture, which is annoying, and search engines gain nothing new from any of them. Each image deserves its own description, specific to what it shows.

The third mistake is keyword stuffing: packing the description with repeated phrases in the hope of ranking for them. Apart from reading terribly aloud, it misdescribes the image, which defeats the entire purpose. One natural mention of the topic, where it genuinely fits the picture, is plenty.

The fourth mistake is describing decorative images at length. A long description of a purely ornamental divider interrupts screen reader users for no benefit. Empty alt text exists for exactly this case, and using it is a sign of understanding, not neglect.

The fifth mistake is forgetting charts and diagrams. A chart image with alt text that says only "chart" tells nobody anything. The description should carry the chart's main finding in a sentence, so a reader who cannot see the chart still learns what it showed. Longer data can go in the surrounding text or in a linked data table, with the alt text summarising the point.

How to apply it step by step to a small-business blog

Start by listing every image in a post before publishing, and sorting them into two groups: images that carry information, and images that are purely decorative. This takes a few minutes and prevents most later errors.

For each informative image, write one or two sentences in plain language. Name the subject first, then the important detail: who or what is shown, what is happening, and any detail the surrounding text relies on. Keep it specific and short. A sentence or two is usually enough; a paragraph is almost always too much.

Next, check the file name. Rename vague names to short, descriptive, hyphenated names that match the image, and keep the file name and the alt text consistent in topic without copying each other word for word. Then, in your editor, paste the description into the alt text field, not into the caption field, unless you also want a visible caption.

Then read each description aloud, or have your screen reader read the page back. Anything that sounds like a list of search phrases should be rewritten as a sentence a person would actually say. Finally, add alt text to your publishing checklist, next to the title tag and meta description, so it is checked on every post rather than remembered occasionally. The metadata generator can help draft the title and description side of that checklist while you write the image descriptions yourself.

For older posts, work backwards from the most-read pages. Open each one, check its images, and fill in the missing descriptions first where the image carries information a reader needs. You do not have to fix an entire archive in one sitting; fixing the posts people actually read gives the best return for the time spent.

How Rankenza handles it

When a Rankenza article includes a photo, the image file name and alt text are written to match the article topic, not stuffed with keywords. Each article starts from research of the top ten search results for its keyword, filtered for search intent, so the images and their descriptions reflect what readers actually looking for that topic expect to see. A human reviews the draft before delivery, including the image descriptions, because a description written for a real reader is something worth checking by eye.

Rankenza articles also use internal links drawn from the customer's own sitemap, so an image-heavy guide can point readers to related posts on the same site rather than leaving them at a dead end. The first article is free, then articles cost $3.60 each or $89 for 50, so a small business can test the approach on one post, including its image descriptions, before committing to more. The SEO blog writing checklist for beginners and the guide on how to write blog posts that rank on Google both cover image descriptions as part of the same publishing routine.

Frequently asked questions

How long should alt text be? One or two sentences is the usual answer. Long enough to describe what matters in the image, short enough to be read aloud without tiring the listener. If you need a paragraph to explain an image, put the longer explanation in the surrounding text and keep the alt text as a summary.

Should every image have alt text? Every informative image should. Decorative images should carry empty alt text so assistive technology skips them. The distinction is about information: if the image adds meaning, describe it; if it adds only decoration, skip it.

Does alt text on its own improve rankings? Not on its own, and no honest writer would promise that it does. It is one part of making a page understandable, alongside good writing, clear headings, and accurate titles. Its main value is for readers, with search understanding as a welcome second benefit.

Can I use the same alt text for the same image on different pages? If it is genuinely the same image showing the same thing, yes, the same accurate description still fits. But if the image is used to make a different point on another page, the description should reflect the point that page is making.

What the research says

According to Google's Image SEO Best Practices documentation, alt text is the most important attribute for providing extra metadata about an image. Google uses alt text together with computer vision and the contents of the page to understand what an image shows, and the same documentation warns against filling alt attributes with keywords, noting that it creates a poor user experience and may cause a site to be seen as spam. That matches the approach taken on this page: describe the picture honestly, in context, and leave keyword lists out of it.

The same documentation also notes that alt text serves readers who cannot see images, including people using screen readers and people on low-bandwidth connections, and that alt text can act as anchor text when an image itself is used as a link. In other words, one short description does three jobs at once: accessibility, understanding, and link meaning. The chart below summarises that contrast qualitatively. It uses no figures, because the source guidance is qualitative: it describes what changes, not by how much.

Chart source note: qualitative comparison based on Google's Image SEO Best Practices documentation (see Sources). No figures are shown because the source gives none for this contrast.

How this looks on Rankenza

On a typical small-business blog, images are uploaded with camera file names and the description field is left empty, so the three jobs above all go undone. On Rankenza's own pages, the approach is the opposite: take the article on image SEO for blog posts, which itself explains the naming and description rules, and the metadata generator, which helps draft the title and description side of the same publishing checklist. Articles start from research of the top ten search results for the keyword, filtered for search intent, and a human reviews the draft before delivery, including image file names and alt text written to match the topic rather than stuffed with phrases. The first article is free, then $3.60 per article or $89 for 50. No traffic or ranking figures are claimed here: the comparison is method against method, and the reader can judge the delivered article itself.

Sources

• Google Search Central, Image SEO Best Practices — alt text as the key image attribute, keyword-stuffing warning, accessibility role.
• Google Search Central, SEO Starter Guide: The Basics — general guidance on making content understandable to search engines and readers.