Alt Text: Describe What Matters
Key takeaways
- Alt text is a textual substitute for an image and supports people using screen readers.7
- Google uses alt text, computer vision and the surrounding page to understand image subject matter.6
- Decorative images can need an empty alt attribute rather than a description.7
- Complex diagrams need a textual explanation beyond a short alt description.7
- Image metadata does not guarantee rankings or inclusion in AI answers.8
What should alt text describe?
Alt text should describe the image's relevant purpose within the surrounding content. The same photograph can need different descriptions on different pages because its role changes.7
For a furniture category page, identify the visible product and a useful distinguishing feature. For an installation guide, explain the visible step. Do not claim a brand, material, certification or location that the image and verified page facts do not establish.
Our recommended test is simple: what useful information would a person miss if the image disappeared? Write that information clearly. The answer is rarely a list of every phrase in the keyword brief, despite the keyword brief's obvious enthusiasm for itself.
How can you avoid keyword stuffing?
Use a keyword only when it naturally helps describe the image. Google's guidance recommends useful, information-rich alt text and warns against filling the attribute with keywords.6
Consider a hypothetical product photograph of a green armchair beside a round table. A useful description might be “Green upholstered armchair beside a round side table.” A poor one would be “Luxury furniture best armchair designer chair buy furniture.” These are illustrative copy examples, not descriptions of a named product.
Do not insert a city just because the business sells there. A chair photographed against a plain backdrop does not suddenly become a documented local installation when someone adds Dubai to its alt text.
When should the alt attribute be empty?
An empty alt attribute can be appropriate when an image is purely decorative or duplicates information already expressed in the text. Google's accessibility guidance distinguishes an empty attribute from an omitted one, which can lead screen readers to announce the filename.7
Record the image's role before making that decision. A divider ornament and an instruction diagram are not equivalent. Avoid replacing every missing description with an empty string merely to make an audit count look healthier.
For functional images, consider what the user needs to understand about the action. Treat the image within its link or control as part of the interface, not as a detached photograph awaiting literary criticism.
How should charts and diagrams be described?
Give a complex image a short alt summary and explain its important information in the page text or a clearly linked longer description. Google's guidance specifically recommends accompanying text for complex graphs, flowcharts and maps.7
A chart should not make its important finding accessible only as pixels. Explain the conclusion and, where useful, provide the underlying data in an accessible form. If the detail cannot fit in a short description, that is a reason to improve the surrounding explanation, not to paste an entire report into an attribute.
This is also a sensible answer-engine practice: important conclusions belong in ordinary text. Google recommends making important content available in textual form for its AI search features.8
Can alt text fix an undiscoverable image?
Alt text alone cannot fix an image implementation that search engines cannot discover. Google says it finds images through the src attribute of HTML img elements and does not index CSS background images.6
Check the delivered and rendered page as well as the CMS field. Google also recommends a fallback src URL when responsive image markup uses picture or srcset.6 A carefully written description that never reaches the published HTML is an editorial achievement with unusually limited distribution.
Keep meaningful images near relevant text, as Google recommends.6 Do not apply this rule indiscriminately to decorative assets: accessibility and search discovery decisions should follow the image's actual purpose.
What should an alt text audit deliver?
An alt text audit should deliver a prioritised inventory with the current attribute, image role, proposed description and an acceptance check. This is our proposed working method, not a claim about a special ranking factor.
Start with commercially important templates: service pages, product categories, product detail pages and instructional articles. For each image, record its page URL, asset URL, visible subject, link or control role, current alt value and whether the value reaches rendered HTML.
Separate missing attributes, inappropriate empty attributes, keyword-stuffed text and inaccurate descriptions. Give product imagery and diagrams human review. Automated suggestions can produce fluent descriptions while confidently identifying an oak finish that nobody has verified.
How should changes be accepted?
Accept a change after reviewing the exact deployed page, its rendered attribute and the image's meaning in context. Keep the before-state and affected template so the change is reversible.
Review performance separately. Image search clicks can indicate discovery, while landing-page engagement and qualified enquiries indicate whether that discovery is useful. Do not attribute every traffic movement to alt text when other page elements changed too.
For connected technical work, read SAGEO's internal-link guide and Core Web Vitals guide. Next step: Scope an image and accessibility audit around your revenue-critical templates, using the SAGEO framework to keep discovery, content and outcomes in one brief.
Limitations
Alt text is one part of accessibility and image understanding. It cannot certify accessibility compliance, compensate for poor page content or guarantee image rankings, AI citations or sales. Google's AI features guidance does not establish how every other answer engine processes images, and no universal LLM behaviour is claimed here.
Sources
[6] https://developers.google.com/search/docs/appearance/google-images, Google Search Central, Image SEO best practices
[7] https://developers.google.com/tech-writing/accessibility/self-study/write-alt-text, Google for Developers, Write helpful alt text
[8] https://developers.google.com/search/docs/appearance/ai-features, Google Search Central, AI features and your website