Alt text should be a short, descriptive sentence that conveys the essential visual information of an image. Keep it under 125 characters, describe only what matters for the context, and avoid starting with "Image of" or "Picture of." For decorative images that add no information, use an empty alt attribute so screen readers skip them.
Why Alt Text Matters for SEO and Accessibility
Search engines cannot see images the way humans do; they rely on file names, surrounding text, and alt attributes to understand visual content. When you write clear alt text, you give crawlers a semantic anchor for the image, which can improve visibility in image search results and contribute to the overall page relevance.
For accessibility, alt text is not optional. Users with visual impairments rely on screen readers to navigate the web. If an image lacks alt text, the screen reader may read the file name (like IMG_4023.jpg) or skip the image entirely, leaving the user with a fragmented experience. Good alt text bridges that gap, ensuring the narrative flow of the page remains intact for everyone.
Core Principles of Effective Alt Text
Keep it concise. Most screen readers cut off alt text after 125 characters, so aim for brevity while retaining meaning. Describe what is important in the image, not everything visible. If the image is decorative and adds no information, use an empty alt attribute (alt="") so screen readers skip it.
Be specific but not redundant. If the caption or surrounding text already says "Our new running shoes," the alt text doesn't need to repeat "Our new running shoes" at the start. Instead, focus on details the text misses, such as color, material, or action. Avoid starting with "Image of" or "Picture of," as screen readers announce that it is an image.
How to Write Alt Text for E-commerce Products
Product pages demand precision. Shoppers using assistive technology need to know exactly what they are considering. Generic file names like shoe.jpg are useless. You need to describe the product’s key features and context.
Consider this step-by-step transformation for a product page:
Original File Name: shoe.jpg Bad Alt Text: shoe Better Alt Text: Red leather running shoes Best Alt Text: Red leather running shoes with white sole on pavement
The best version describes the color, material, and a contextual detail (the sole and setting) that helps the user visualize the product. It includes keywords like "running shoes" and "red leather" naturally.
Here is how you might structure this in HTML:
<img src="red-running-shoes.jpg"
alt="Red leather running shoes with white sole on pavement"
width="600"
height="400">For a catalog with hundreds of items, writing these manually is time-consuming. However, the principle remains: describe the object, its attributes, and its context. If the image shows a model wearing the shoes, mention that context if it adds value, such as "Red leather running shoes worn by a runner on a trail."
Writing Alt Text for Blog Images and Context
Blog images serve a different purpose. They illustrate concepts, break up text, or provide visual evidence. The alt text should relate to the specific paragraph or section where the image appears.
For example, if you have a blog post about "How to Bake Sourdough Bread," an image of a loaf should not just say "bread." It should say something like "Crusty sourdough loaf sliced open to show airy crumb structure." This tells the user what aspect of the bread is important to the article.
If the image is a chart or graph, the alt text should summarize the main takeaway. For a bar chart showing sales growth, use "Bar chart showing sales increase in Q3 compared to Q2." Do not just say "Sales chart." The user needs the data insight, not just the format.
Common Mistakes to Avoid
One major mistake is keyword stuffing. Writing "Best red running shoes cheap red running shoes sale red running shoes online" looks like spam to search engines and is annoying for screen reader users. Keep it natural.
Another error is describing the image file rather than the content. Avoid "JPG image of a dog." The screen reader already tells the user it is an image. Just say "Golden retriever playing fetch in a park."
Also, do not ignore decorative images. If a separator line or a background texture adds no information, mark it as decorative. In HTML, this is done with an empty alt attribute:
<img src="decorative-line.png" alt="">If you leave the alt attribute out entirely, some screen readers will read the file name, which is confusing. An empty alt attribute explicitly tells the screen reader to ignore the image.
Automating Alt Text Generation at Scale
Writing alt text for thousands of products or blog posts is a bottleneck for many teams. Manual entry is slow and prone to inconsistency. This is where automation can help, provided you maintain quality control.
When scaling, you need a solution that understands context. Generic tools might describe a product photo as "a shoe on a white background," which is accurate but not useful for SEO or user experience. You want descriptions that distinguish the product from the background and include relevant details.
AltTextAI generates WCAG-compliant descriptions by analyzing the visual content in context. It distinguishes products from backgrounds to create accurate descriptions and integrates relevant keywords naturally for SEO. This ensures that as you process thousands of images in bulk, the output remains unique and compliant.
For developers, integrating this into a CMS or e-commerce platform is straightforward. You can push generated alt text directly to your site via API. This workflow allows you to upload a catalog, generate descriptions in seconds, and deploy them without manual tagging.
However, automation is not a "set it and forget it" solution. Always spot-check a sample of the generated text. Ensure it matches your brand voice and accurately reflects the image. For critical pages, manual review is still recommended. For the bulk of your library, automated generation frees up your team to focus on higher-value tasks while maintaining accessibility standards.