How to Audit Image Alt Text: Technical SEO and Accessibility Guide

Visual assets form the creative core of modern websites, engaging human visitors, highlighting product details, and reinforcing complex editorial concepts. However, search engine algorithms and assistive screen readers cannot see image pixels the way humans do. Instead, they rely on the HTML alt attribute (alternative text) to interpret what an image depicts, how it relates to surrounding copy, and whether it qualifies for visual search features like Google Images.

Despite being a foundational element of on-page search engine optimization and digital accessibility compliance, image alternative text is frequently neglected. Content teams and developers often leave alt attributes empty, populate them with uninformative camera file names, or stuff them with repetitive commercial keywords. Learning how to audit image alt text across your domain ensures that your media library remains fully accessible, compliant with accessibility standards, and positioned to drive organic traffic from visual and traditional search results.

What Is Image Alt Text and Why Does It Matter?

Image alt text is an attribute applied inside an HTML image tag (<img src="..." alt="...">). It fulfills three critical functions across the web:

• Accessibility and Assistive Technology: Visually impaired users relying on screen readers hear the alt text read aloud. If the alt attribute is missing, the screen reader may announce the raw, messy image file name instead, creating a frustrating user experience.
• Image Search Indexation and Ranking: Googlebot uses alt text alongside computer vision algorithms and page context to understand image subject matter. Well-crafted alt text is the primary on-page signal for ranking in Google Images.
• Network Fail-Safe Display: If a user experiences a slow mobile connection or an image asset fails to load from a Content Delivery Network (CDN), the browser displays the alt text inside the broken image container.

The 5 Most Common Image Alt Text Errors

During technical audits, media inventories typically exhibit recurring alt attribute mistakes:

Informative vs. Decorative Images: The Null Alt Rule

A crucial rule of Web Content Accessibility Guidelines (WCAG) that many SEO teams overlook is distinguishing between informative images and decorative images:

• Informative Images: Product photos, infographics, team portraits, diagrams, and illustrative screenshots convey real meaning. These require descriptive alt text that explains the visual content accurately.
• Decorative Images: Abstract background shapes, stylistic divider lines, spacer graphics, and decorative flourish icons provide visual flair without adding information. These should have a blank, null alt attribute: alt="". This instructs screen readers to skip them quietly rather than interrupting the audio flow.

Step 1: Crawl Your Complete Media Inventory

To inspect alt text across thousands of assets simultaneously, execute a crawl using an industry-standard technical crawler such as Screaming Frog SEO Spider, Sitebulb, or an enterprise auditing platform:

1. Open your crawler and ensure extraction settings for Images are active under crawl configuration.
2. Enter your primary domain URL (e.g., https://www.yourdomain.com) and begin the crawl.
3. Once the crawl finishes, navigate to the Images tab in the navigation menu.
4. Review the built-in filters:
   • Missing Alt Text: URLs where the <img> tag completely lacks an alt attribute.
   • Alt Text Over 100 Characters: Images where the description is excessively long and should be condensed.
5. Export the image crawl dataset into a spreadsheet to begin systematic categorization.

Step 2: Filter and Evaluate Alt Text Quality

Raw crawler filters only detect whether an alt attribute exists. An effective audit requires reviewing the actual text strings to ensure quality and relevance:

1. Flag Camera File Names and File Extensions

In your exported spreadsheet, filter the alt text column for strings containing .jpg, .png, .webp, DSC_, IMG_, or screenshot. Replace these automated CMS placeholders with accurate natural language descriptions.

2. Identify and Purge Keyword Stuffing

Look for repetitive strings of commercial keywords forced into product images. For instance, an image showing a blue leather sofa should read alt="Navy blue three-seater leather sofa with wooden legs" rather than alt="buy couch cheap sofa furniture online sale".

3. Check for Broken Image References

Cross-reference your image report with HTTP response codes. If an image returns an HTTP 404 Not Found error, remove the image reference or replace the broken source file to prevent wasted crawl requests and broken layout containers.

Step 3: Apply the Formula for High-Quality Alt Text

When rewriting missing or low-quality image descriptions, follow these writing guidelines:

• Be Specific and Objective: Describe the visible elements of the image clearly (colors, subjects, actions, settings).
• Keep It Concise: Aim for 80 to 125 characters. Screen readers typically cut off or pause reading after approximately 125 characters.
• Incorporate Primary Keywords Naturally: Include your target topic only if it naturally represents what is shown in the image.
• Omit Redundant Words: Do not include phrases like "image of", "photo of", or "graphic showing". Screen readers automatically announce the element as an image before reading the text.

Before and After Writing Examples:

• Bad: alt="shoes" (Too vague)
• Bad: alt="buy running shoes best men running shoes sale" (Keyword-stuffed)
• Good: alt="Men's lightweight black mesh running shoes with white foam soles" (Specific, natural, accessible)

Step 4: Audit Alt Text on Hyperlinked Images

When an image is wrapped inside an anchor tag (<a href="..."><img src="..." alt="..."></a>), the image's alt text acts as the hyperlink anchor text for search engine crawlers and screen readers.

• If a linked image has empty alt text (alt=""), crawlers cannot tell where the link leads, and screen readers will announce an inaccessible empty link or read the raw destination URL.
• Ensure linked logo images, banner buttons, and call-to-action cards feature clear, destination-oriented alt text (e.g., alt="BrandStory Home" for a linked homepage logo).

Step 5: Verify XML Image Sitemaps

To help search engine bots discover and index your visual assets efficiently, audit your dedicated image sitemaps alongside your HTML code:

• Ensure your sitemap includes valid image extension tags:

  <url>
    <loc>https://www.yourdomain.com/products/running-shoe/</loc>
    <image:image>
      <image:loc>https://www.yourdomain.com/images/running-shoe-black.jpg</image:loc>
      <image:title>Men's Lightweight Running Shoe in Black</image:title>
      <image:caption>Breathable black mesh athletic shoe with cushioned sole.</image:caption>
    </image:image>
  </url>

• Confirm that image URLs hosted on external CDNs are authorized within your Google Search Console property or verified via CNAME custom domain records.

Professional Technical Execution for Enterprise Platforms

For high-inventory e-commerce stores, dynamic digital marketplaces, and enterprise publishers managing hundreds of thousands of visual assets, writing alt text manually across legacy databases is impractical. Partnering with a dedicated seo agency in Dubai allows brands to configure automated database rules, clean up programmatic template flaws, and deploy accessibility-compliant metadata at scale across competitive regional and international markets.

Image Alt Text Audit Checklist

Use the checklist below to verify the quality of your visual assets before completing your audit:

Maintain Continuous Visual Media Quality

Auditing image alt text bridges the gap between technical search engine optimization and inclusive web accessibility. By eliminating missing attributes, replacing camera file names with descriptive copy, removing keyword stuffing, and setting null tags on purely decorative graphics, you ensure search engines can index your visual assets accurately while providing an accessible experience for all visitors.