What Is Image Alt Text?
Image alt text, short for alternative text, is the text content of the alt attribute on an HTML image element. When you add an image to a web page, the image tag includes an alt attribute where you write a brief description of what the image shows. This text serves as a textual replacement for the image in situations where the image cannot be displayed, such as when the image file fails to load, when a user has images disabled in their browser, or when a visually impaired user is navigating the page with a screen reader. The screen reader reads the alt text aloud, allowing the user to understand what the image depicts.
The alt attribute has been part of the HTML specification since its early days, and it is a required attribute on image elements according to web accessibility standards. Despite this, missing alt text remains one of the most common issues found on websites across every industry. The WebAIM Million study, which analyzes the top one million home pages annually, consistently finds that missing alt text on images is the most prevalent accessibility error on the web. For small business owners, this means that adding proper alt text to your images immediately puts you ahead of a large portion of websites in terms of both accessibility compliance and SEO optimization.
Search engines cannot see images the way humans do. While Google has made advances in image recognition technology, it still relies heavily on the alt text to understand what an image contains and how it relates to the surrounding content. The alt text is the primary signal Google uses to index images for Google Images search results, which drives meaningful traffic to many small business websites. A local photographer, restaurant, landscaper, or retail store can receive significant visibility through Google Images if their photos have descriptive, keyword-rich alt text. Without alt text, your images are essentially invisible to search engines.
Why Alt Text Matters for SEO and Accessibility
From an SEO perspective, alt text provides search engines with context about your images that they cannot derive from the image file alone. Google uses alt text as a ranking signal for Google Images search, which accounts for approximately 22 percent of all Google searches. If you run a bakery and your product photos have alt text like "custom three-tier wedding cake with white fondant and pink roses," those images can appear when potential customers search for wedding cakes in Google Images. Each image that ranks in Google Images is a potential entry point to your website, driving traffic that you would miss entirely if your images had no alt text.
Alt text also reinforces the topical relevance of the page where the image appears. When Google analyzes a page about kitchen renovations and finds images with alt text describing "modern kitchen with white quartz countertops" and "hardwood floor installation in open kitchen," it gains additional confidence that the page is genuinely about kitchen renovations. This contextual reinforcement can modestly improve the page's ranking for related keywords. Conversely, images with missing or generic alt text like "image1.jpg" or "photo" represent missed opportunities to strengthen your page's topical signals.
Accessibility is not just an ethical consideration but increasingly a legal one. In many jurisdictions, including the United States under the ADA, websites must be accessible to users with disabilities. Lawsuits related to web accessibility have increased dramatically in recent years, and missing alt text is one of the most cited violations. Beyond legal compliance, making your website accessible expands your potential audience. Approximately 15 percent of the global population has some form of disability, and many more people encounter situations where alt text is useful, such as slow internet connections where images fail to load or email clients that block images by default. Writing good alt text is a small investment that serves a large and diverse audience.
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How to Write Effective Alt Text
Effective alt text is descriptive, specific, and concise. It should accurately describe what the image shows in enough detail that someone who cannot see the image gets a clear mental picture. For a photo on a restaurant website, instead of writing "food" as the alt text, write "grilled salmon fillet with roasted vegetables and lemon butter sauce on a white plate." The second description tells both screen reader users and search engines exactly what the image depicts. Aim for alt text between 10 and 125 characters, though this is a guideline rather than a hard rule. The key is to be descriptive without being unnecessarily verbose.
Include your target keyword in alt text when it is naturally relevant to the image, but do not force keywords into every image description. If you run a plumbing business and the image genuinely shows a plumber fixing a kitchen faucet, then "licensed plumber repairing a leaking kitchen faucet in a residential home" is excellent alt text because it is both descriptive and naturally incorporates relevant keywords. However, if the image is a headshot of your team, the appropriate alt text would be "portrait of John Smith, lead plumber at ABC Plumbing" rather than stuffing in "best plumber in Chicago" which would be irrelevant to the actual image content.
Different types of images call for different alt text approaches. Decorative images that serve no informational purpose, such as background patterns, decorative dividers, or purely aesthetic flourishes, should have an empty alt attribute (alt="") which tells screen readers to skip them entirely. Informational images like product photos, charts, diagrams, and illustrative photographs need descriptive alt text. Images that function as links or buttons need alt text that describes the action or destination rather than the image content. For example, a social media icon linking to your Facebook page should have alt text like "Visit our Facebook page" rather than "Blue Facebook logo." Understanding these distinctions helps you write alt text that genuinely serves users and search engines rather than applying a one-size-fits-all approach.
Common Alt Text Mistakes
The most prevalent alt text mistake is leaving the alt attribute completely empty or omitting it entirely from image tags. This creates images that are invisible to screen readers and provide zero SEO value. Many website owners are not even aware that their images lack alt text because the visual presentation of the page is unaffected. It is only when you inspect the HTML source code or run an accessibility audit that missing alt attributes become apparent. CMS platforms do prompt you to add alt text when uploading images, but many users skip this field because they do not understand its importance or are in a hurry to publish content.
Keyword stuffing in alt text is the opposite extreme and equally problematic. Some site owners believe that cramming multiple keywords into every alt attribute will boost their rankings. An alt text like "best plumber cheap plumbing service emergency plumber near me affordable plumber" does not describe any image and reads as pure spam to both users and search engines. Google specifically warns against keyword stuffing in alt text and may view it as an attempt to manipulate search rankings. Overstuffed alt text can trigger manual actions or algorithmic penalties that hurt your site's visibility rather than help it. One naturally placed keyword in alt text that accurately describes the image is all you need.
Using generic or auto-generated alt text is another widespread issue. Alt text like "IMG_3847.jpg," "image," "photo," "screenshot," or "untitled" provides virtually no information about the image content. Some CMS platforms auto-generate alt text from the filename when none is provided, resulting in alt text like "hero-banner-final-v2" which is meaningless to both users and search engines. Similarly, using the same alt text for every image on a page or across your site misses the point entirely. Each image on your website depicts something unique, and the alt text should reflect that uniqueness. Take the time to write individual, descriptive alt text for every meaningful image on your site, especially product images, team photos, portfolio items, and any image that contributes to the page's content and message.
How Lumio SEO Audits Image Alt Text
Lumio SEO scans every image on your page and evaluates its alt attribute as part of its on-page SEO and accessibility checks. The tool identifies three categories of alt text issues: images with completely missing alt attributes, images with empty alt attributes that should have descriptive text, and images with alt text that contains quality problems such as excessive length, keyword stuffing, or generic placeholder text. Each issue is listed with the specific image URL and its current alt text value, making it straightforward to locate and fix every problematic image.
The tool distinguishes between decorative images and content images in its analysis. Decorative images that have an intentionally empty alt attribute (alt="") are treated differently from content images that are missing alt text entirely. This nuanced approach prevents false positives where a developer has correctly marked a decorative spacer or background image with an empty alt. For content images that should have descriptive text, Lumio SEO provides the image URL and its context on the page, helping you write appropriate alt text even if you are not looking at the page in a browser at that moment.
For site-wide audits, Lumio SEO aggregates alt text issues across all analyzed pages and provides a comprehensive report. This report reveals patterns such as entire page templates where the featured image consistently lacks alt text, product categories where image descriptions are missing, or sections of the site where auto-generated alt text from filenames is prevalent. The aggregate view helps small business owners prioritize fixes based on the number of affected pages and the importance of those pages to their SEO strategy. Fixing alt text on your twenty most-visited pages first provides the greatest immediate return, and Lumio SEO helps you identify exactly which pages those are. The tool also tracks alt text improvements over time, so you can verify that your fixes are holding and that new content is being published with proper alt attributes.