Alt text is one of the most consistently misunderstood elements of on-page SEO. Many creators either skip it entirely ("the image speaks for itself"), stuff it with keywords, or write generic descriptions that serve neither accessibility nor search engines. Done correctly, alt text is a dual-purpose tool: it makes your content accessible to users with visual impairments and gives Google the contextual signal it needs to surface your images in relevant search results.
Alt text — short for "alternative text" — is the HTML attribute that describes an image to contexts where the image itself cannot be seen or processed. This includes screen readers used by visually impaired users, search engine crawlers that index image content, email clients with images disabled, and page loading states where images fail to render.
Screen readers like JAWS and NVDA read alt text aloud to blind and low-vision users. When alt text is absent or unhelpful ("image1.jpg" or "photo"), these users receive no information about the visual content. Web Content Accessibility Guidelines (WCAG) 2.1 requires meaningful alt text for all informational images, and in many jurisdictions, inaccessible websites create legal liability. Good alt text is not optional — it is a baseline requirement for any professional web presence.
Google Images is one of the most visited search surfaces on the internet. Images with precise, keyword-aware alt text consistently outperform images with empty or generic alt attributes in Google Images search rankings. Beyond images search, alt text contributes to the overall relevancy signal of the page it appears on — helping pages rank in regular web search for their target keywords when the images reinforce the topic.
Google's image search algorithm combines alt text with surrounding page content, the image file name, the page URL, and structured data to understand what an image depicts. Alt text is the strongest of these signals because it is the most direct human-controlled description of image content.
Rather than guessing what to write, use a structured formula that satisfies both accessibility and SEO requirements simultaneously.
For a product photo of a ceramic coffee mug on a wooden table in a kitchen setting, targeting the keyword "handmade ceramic coffee mug":
Overhead photo of a handmade ceramic coffee mug on a reclaimed wood table in a bright kitchen setting
This description tells a screen reader user exactly what they are missing. It tells Google this is a product photo, identifies the specific product ("handmade ceramic coffee mug"), and grounds it in a contextual setting. The keyword "handmade ceramic coffee mug" appears naturally without stuffing.
coffee mug ceramic mug handmade mug pottery mug gift mug — this reads as spam to both screen readers and Google.alt="" is appropriate only for purely decorative images. For any image that conveys meaning or content, empty alt text is incorrect both technically and for SEO.DSC_4821.jpg or product-photo-3.jpg are not alt text. Rename image files to descriptive slugs (e.g., handmade-ceramic-coffee-mug.jpg) and write alt text separately.The widely cited guideline is 125 characters — this comes from older screen reader limitations that would truncate alt text at that point. Modern screen readers handle longer alt text, but 125 characters remains a useful discipline because it forces specificity and prevents rambling.
In practice, most effective alt text falls between 80 and 125 characters. This is enough to be descriptive, include a natural keyword, and provide context — without becoming a paragraph that overwhelms the text flow for screen reader users.
When to write longer alt text: for complex informational images like charts, infographics, maps, and diagrams, 125 characters is often insufficient to convey the meaningful content. In these cases, a longer alt text or a supplementary longdesc attribute or adjacent visible description is appropriate. The goal is always to give non-visual users the same information the image communicates to visual users.
| Attribute | Where It Appears | SEO Weight | Accessibility Role |
|---|---|---|---|
| Alt text | HTML alt attribute, invisible to most users | High | Primary — read by screen readers |
| Image title | Tooltip on hover (most browsers) | Very low | Supplementary — rarely read by screen readers |
| Caption | Visible below the image | Moderate (page context) | Visible to all users including screen reader users |
| File name | URL, source attribute | Low-moderate | None |
Alt text and caption should not be identical. Alt text describes what the image shows. A caption provides editorial context — why this image is here, what it means in the context of the surrounding content. If your article caption says "Our bestselling ceramic mug, available in four glazes," your alt text should describe the visual: "Close-up of a teal-glazed handmade ceramic mug with a matte finish on a white background."
Use the alt attribute within the img tag: <img src="image.jpg" alt="Your description here">. For decorative images that add no informational value (borders, spacers, purely aesthetic flourishes), use alt="" to indicate intentional omission to screen readers.
WordPress surfaces the alt text field in the media library under "Alternative Text" for each uploaded image. It also appears in the image block editor under the image settings panel. Set alt text in the media library for images used across multiple pages so the description carries through everywhere the image is used. Override it per placement when context-specific description is needed.
Etsy allows alt text on listing photos added from the listing edit page. Most sellers don't use this field, which means it's a significant competitive advantage for those who do. Etsy listing photo alt text contributes to both Etsy internal search and Google's indexing of Etsy listing pages. Treat it exactly like standard HTML alt text — describe the product specifically, include the primary keyword naturally.
Instagram allows you to add alt text when posting images. In the post creation flow, go to Advanced Settings and find "Write Alt Text." Instagram auto-generates alt text using AI if you don't add custom text — the auto-generated version is generic and not keyword-optimized. Adding custom alt text improves accessibility for Instagram's screen reader users and may influence how the post appears in Instagram and Google search results.
AI-powered alt text generation solves one of the most time-consuming parts of image SEO at scale. For a site with hundreds or thousands of images, manually writing individualized alt text for every image is impractical. Vision-capable AI tools analyze image content and generate descriptions that satisfy both the accessibility formula and keyword relevancy requirements.
The key to effective AI alt text generation is providing keyword context. An AI tool that knows the target keyword for a page — or the primary product keyword for an e-commerce listing — can weave that keyword into an accurate descriptive alt text rather than generating a purely generic description. The output is "Flat lay photo of handmade ceramic coffee mug with blue glaze on white marble surface" rather than "A cup on a surface."
Review AI-generated alt text before publishing. Check that the description is factually accurate for the specific image (AI can misidentify objects, colors, or settings), that the keyword inclusion reads naturally rather than forced, and that the length falls within the 80–125 character target range.
If your site has been live for more than a year without consistent alt text practices, an audit is one of the highest-ROI SEO activities you can perform. Here's a systematic approach:
Use a site crawler (Screaming Frog's free version handles up to 500 URLs) to export a list of all images on your site along with their alt text values. Filter for blank alt text, single-word alt text, or alt text that exactly matches the file name — all three patterns indicate missed optimization.
Fix images on your highest-traffic pages and most commercially important product pages first. A missing alt text on your homepage hero image or primary product photos costs more in lost ranking potential than missing alt text on a blog sidebar image from three years ago.
Write alt text using the [image type] + [subject] + [context] + [keyword qualifier] formula. Focus on accuracy first, keyword integration second. An accurate alt text with no keyword is better than a keyword-stuffed alt text that doesn't describe the image.
While you're in the media library, rename vague file names to keyword-descriptive slugs. Use hyphens between words (not underscores, which Google does not parse as word separators). handmade-ceramic-coffee-mug-teal-glaze.jpg is better than DSC_4821.jpg on every SEO metric.
Upload your image and let Metadata Reactor generate accurate, keyword-aware alt text that follows the accessibility and SEO best practices in this guide — ready to copy and paste.
Try the Alt Text Generator Free →alt=""). This tells screen readers to skip the image rather than announcing it, which improves the reading experience for visually impaired users. Only apply descriptive alt text to images that convey meaningful content.