Alt text is the short written description attached to an image in your site's code. Search engines read it to understand what the picture shows, and screen readers speak it aloud to people who cannot see the image. Writing it well costs almost nothing and improves two things at once: how your images rank, and whether your site is usable by everyone.
What Is Image Alt Text?
Image alt text, also called alternative text or an alt tag, is a brief description of an image's content stored in the HTML alt attribute. It serves two audiences that never see each other: search engine crawlers, which cannot interpret a photograph but can read a sentence about it, and people using assistive technology, for whom that sentence is the image.
A related but different field is the image title attribute, which some browsers show as a tooltip on hover. Alt text is the one that matters for both SEO and accessibility; the title attribute is optional and often best left empty rather than filled with a duplicate.
Why Do Image Titles and Alt Text Matter for SEO?
Because a search engine cannot see. Alt text is the primary signal telling a crawler what an image depicts, which is what lets it index the image, show it in image search, and use it as one more piece of evidence about the topic of the page it sits on. Pages with images that carry no alt text lose that evidence entirely, and in competitive categories that difference is measurable.
Two principles govern good alt text:
Be concise and specific. Describe what is actually in the image, in a phrase rather than a paragraph. Aim for roughly 8 to 15 words.
Include a keyword only when it belongs. A relevant term helps a crawler place the image in context. A term forced in against the actual content of the picture helps nobody and risks being read as manipulation.
Alt text is particularly important for multilingual SEO across Europe, where the same image sits on several language versions of a page and each one needs its description written in that language rather than copied from the original.
How to Write Alt Text, Step by Step
Start by looking at the image and deciding what it is actually for on that page. A product photo, a diagram and a decorative background have three different jobs, and their alt text should differ accordingly.
Product images: describe the product as a customer would recognize it. "Red steel bicycle with leather saddle" beats "bicycle" and beats "buy bicycle online cheap".
Diagrams and charts: state what the diagram shows, not that it is a diagram. If it carries data the reader needs, put that data in the surrounding text as well, because alt text is too short to hold it.
Photos of people or places: describe the scene in the terms a reader would use. Context matters more than detail.
Purely decorative images: leave the alt attribute empty (
alt=""). This is deliberate and correct: it tells a screen reader to skip an image that carries no information, instead of reading out a filename.
Best Practices and Common Mistakes
Most alt text problems fall into four categories:
Leaving alt text off entirely. The image conveys nothing to a crawler and is announced as an unlabeled graphic to a screen reader.
Placeholder text. "image1", "DSC_0043" or "photo" describe nothing and waste the attribute.
Keyword stuffing. A string of search terms degrades the experience for assistive technology users and is treated as a spam signal.
Descriptions that do not match the image. Misleading alt text damages accessibility and credibility at the same time, and it is surprisingly common on sites where alt text was written from a keyword list rather than from the pictures.
The underlying rule is simple: write the description first for a person who cannot see the image, then check whether a relevant keyword fits naturally. Doing it in the opposite order produces text that serves neither audience.
Monitoring Alt Text Performance
Once alt text is in place, check that it is doing something. Look at impressions and clicks from image search in Google Search Console, watch whether your images start appearing for the queries you expected, and run periodic crawls to catch images added later with no alt attribute at all. On a site with an active blog or catalog, missing alt text reappears constantly, which makes this an audit to repeat rather than a task to complete once.
Getting Image SEO Right, at Scale
Alt text is one of the few improvements that raises visibility and accessibility with the same edit. On a site with a handful of pages it is an afternoon's work. On a catalog with thousands of images, in several languages, it becomes a process that needs rules, templates and checks.
At Mintense we have spent more than 17 years and over 200 SEO and PPC projects on exactly this kind of detail. We are a certified Google Partner and Microsoft Advertising Partner, with offices in Verona, Lille and London, and we work with companies selling across the United States and Europe. If you want your images working for you rather than sitting there silently, get in touch.
Frequently Asked Questions
What is the difference between alt text and an image title?
Alt text lives in the HTML alt attribute and describes what the image shows; it is read by search engines and by screen readers, and it is the one that affects SEO and accessibility. The title attribute is a separate field that some browsers display as a tooltip on hover. It is optional, invisible to most users, and usually better left empty than filled with a copy of the alt text.
How long should alt text be?
Roughly 8 to 15 words is a good target, and around 125 characters is a practical upper limit because some screen readers truncate beyond that point. The real test is whether someone who cannot see the image would understand what it shows from your sentence alone. If the image carries information that needs more words than that, put it in the page text where everyone can read it.
Should every image have alt text?
Every image that carries meaning should. Purely decorative images, such as background textures or spacer graphics, should have an empty alt attribute written as alt equals two quotation marks with nothing between them. That is not the same as omitting the attribute: an empty alt tells assistive technology to skip the image, while a missing one leaves the screen reader to announce a filename.
Does alt text actually improve search rankings?
It improves how well your images rank in image search, which for visual categories can be a meaningful traffic source in its own right. It also gives search engines additional context about the page the image sits on. It is not a large ranking factor on its own, and no single image will move a page, but on a site with hundreds of images the cumulative effect is real and the cost of doing it is close to zero.
Do I need different alt text for each language version of a page?
Yes. Alt text is content, so a page served in German needs alt text in German, just as it needs its headings and body copy in German. Leaving the original language in place on translated pages is one of the most common oversights we find on multilingual sites, and it means those images contribute nothing to visibility in that market.
Can AI generate alt text for my images?
It can produce a reasonable first draft, especially for straightforward product photography, and that is genuinely useful on a large catalog. What it cannot reliably do is know why a particular image is on a particular page, which is what separates adequate alt text from good alt text. Treat generated descriptions as a starting point to review rather than as finished output.
