Alt text is a short, descriptive sentence that tells screen-reader users and search engines what an image shows. Write it by naming the subject, noting its color or material, and describing its setting—then keep it under 125 characters.
Why Alt Text Matters for SEO and Accessibility
Alt text serves two audiences at once. Screen-reader users rely on it to understand what an image shows when they cannot see it. Search engines use it to understand the content of images that cannot be indexed visually. Good alt text improves both experiences without requiring separate descriptions.
When alt text is missing, screen readers often read the filename instead, which produces confusing results like "IMG_4521.jpg." Search engines may ignore the image entirely in image-search results. Writing clear alt text solves both problems simultaneously and requires no additional markup beyond the standard alt attribute.
Core Principles of Effective Alt Text
Effective alt text answers one question: what does this image show? Keep descriptions factual and specific. Name the subject, mention distinguishing features like color or material, and note the background or setting if it adds meaning. Avoid decorative language, promotional copy, or phrases like "image of" or "photo of," since screen readers already announce that an image follows.
Length matters. Aim for a single sentence between 5 and 125 characters. Longer descriptions risk being truncated by assistive technology. If an image needs a longer explanation, place that text in the surrounding paragraph rather than in the alt attribute.
For decorative images—purely ornamental borders, spacer graphics, or repeated icons—use an empty alt attribute (alt=""). This tells screen readers to skip the element entirely, reducing noise for users who rely on audio navigation.
Step-by-Step: Writing Alt Text Manually
Start with the most specific noun that identifies the subject. Add one or two modifiers that distinguish this instance from similar items. End with context if the setting changes how the image should be understood.
Consider a product photo of a red leather handbag with a gold buckle, photographed against a plain white background. A weak alt text reads simply "bag." It lacks color, material, and distinguishing detail. A stronger version reads:
Red leather handbag with gold buckle on white backgroundThis sentence names the object (handbag), its color and material (red leather), its distinguishing feature (gold buckle), and its setting (white background). It stays under 125 characters and gives a screen-reader user a complete mental picture.
When writing manually, ask yourself whether someone hearing only the description could sketch a reasonable approximation of the image. If yes, the alt text works. If the description feels vague, add one concrete detail until it clicks.
Automating Alt Text Generation at Scale
Manual writing works well for a handful of images. Catalogs with hundreds or thousands of product photos demand a different approach. Bulk generation tools analyze each image, identify the subject and background, and produce a concise description tailored to the visual content.
For example, uploading 50 product photos of similar handbags in varying colors produces 50 unique descriptions rather than one generic tag applied across the board. Each output reflects the specific hue, hardware finish, and backdrop visible in that particular photo. This consistency matters because shoppers and search engines treat each variant as distinct.
AltTextAI processes bulk uploads in seconds and returns WCAG-compliant descriptions for every image in the batch. You can review the outputs, adjust any that need refinement, and deploy them directly to your site. For teams managing large catalogs, this removes the bottleneck of writing each caption by hand. Try it at AltTextAI.
Integrating Alt Text into Your CMS
Once descriptions exist, getting them onto your site should not require opening each image individually. Most content management systems accept alt text through their media library or a dedicated field in the editor. For larger catalogs, an API connection pushes descriptions programmatically, saving time on repetitive entry tasks.
A typical integration follows three steps: upload your image batch, generate descriptions, then sync them back to your platform. Many e-commerce platforms and blogging systems expose endpoints that accept alt text in JSON format. Here is a simplified example of how an API call might look:
{
"image_id": "prod_4821",
"alt_text": "Red leather handbag with gold buckle on white background"
}Your platform ingests this payload and attaches the description to the corresponding image record. Repeat across your catalog and every image carries meaningful alt text without manual intervention. If your CMS lacks native bulk-import support, a developer can script this loop in minutes using standard HTTP requests.
Common Mistakes to Avoid
Several patterns undermine alt text quality. Watch for these during review cycles.
- Keyword stuffing. Repeating brand names or search terms inside alt text dilutes its usefulness. Write for humans first; search engines reward clarity, not density.
- Over-describing. Listing every minor detail overwhelms screen-reader users. Stick to what distinguishes the subject from similar items.
- Under-describing. A single word like "bag" or "logo" leaves the user guessing. Add at least one distinguishing detail.
- Decorative images with alt text. Ornamental dividers and spacer graphics should use
alt=""so assistive technology skips them silently. - Copying the caption. Alt text and captions serve different purposes. Captions appear visually below images; alt text is read aloud or parsed by crawlers. Keep them separate.
Review your alt text quarterly, especially after adding new product lines or redesigning templates. Consistency across the site matters more than perfection on any single image. When in doubt, read the description aloud: if it sounds natural and informative, it likely works for both audiences.