How to Check WCAG Compliance for Image Alt Text

WCAG compliance for image alt text means every meaningful image has a concise, accurate description that conveys its purpose, while decorative images are marked as presentational. To check compliance, you must verify that text alternatives exist, are descriptive rather than generic, and avoid keyword stuffing, ensuring the text serves the same purpose as the visual.

Why WCAG Compliance Matters for Images

Screen readers cannot see pixels; they read code. If an image lacks a text alternative, the screen reader often reads the filename, which is rarely helpful. If the alternative is explicitly set to empty (alt=""), the image is typically treated as decorative and skipped entirely. This creates a fragmented experience for users with visual impairments.

Beyond accessibility, alt text supports search engine optimization by providing context to crawlers. However, the primary driver for checking compliance is legal and ethical risk reduction. Many organizations face pressure to meet accessibility standards to avoid litigation and ensure inclusive user experiences. The goal is functional equivalence: a user relying on assistive technology should understand the content and function of the image as effectively as a sighted user.

The 5 Key WCAG Criteria for Alt Text

You do not need to memorize the entire WCAG specification. For images, focus on these five practical rules derived from WCAG 2.1 Level A and AA success criteria.

1. Presence: Every image that conveys information must have a text alternative. This is typically an alt attribute on an <img> tag, but can also be achieved via ARIA labels or surrounding text depending on the implementation.
2. Descriptiveness: The text must describe the content and function of the image, not just the file type or name.
3. Conciseness: Keep descriptions short. Long alt text is cumbersome to listen to. If a detailed description is necessary, use a long description attribute or link to nearby text.
4. Decorative Handling: Images used solely for visual appeal must have an empty alt attribute (alt="") so screen readers skip them.
5. No Redundancy: Do not repeat information already in the surrounding text or caption. Do not include "image of" or "graphic of" in the alt text, as screen readers already announce the element type.

Manual Checklist: How to Audit Your Alt Text

Start with a manual audit of a representative sample of pages. This helps you understand the specific patterns your team is using. Open your browser’s developer tools and inspect the <img> tags.

Look for these specific failures:

• Missing Alt: The alt attribute is absent entirely.
• Empty Alt on Content Images: The alt attribute exists but is empty (alt="") on an image that contains text or essential product details.
• Generic Alt: The text says "photo," "image," "banner," or "logo" without context.
• Filename as Alt: The alt text is IMG_0423.jpg or similar.
• Keyword Stuffing: The alt text is a list of keywords separated by commas, such as "blue dress, summer dress, women's fashion, cheap dress."

For each image, ask: "If I removed this image, would I lose information?" If yes, it needs descriptive alt text. If no, it should be decorative.

Using Automated Tools to Check Compliance

Manual audits are accurate but slow. Automated tools can scan entire sites to identify obvious errors. These tools are excellent for finding missing alt attributes and flagging suspicious patterns like excessive length or keyword density.

However, automated tools cannot judge semantic accuracy. They can tell you that "image" is a bad alt text, but they cannot tell you if "Red running shoe on pavement" is accurate for the specific photo. Use automation to find the volume of errors, then use manual review to verify the quality of the descriptions.

When evaluating tools, look for those that distinguish between decorative and informational images. A good tool will flag empty alt tags on images with complex dimensions or those placed near headings, suggesting they might be informational.

Common WCAG Failures in E-commerce and Blogs

E-commerce sites and blogs have distinct failure patterns. In e-commerce, missing alt text, low contrast, and form-label issues are frequently reported. For example, a product page might have five images of a shirt, but all five have alt="shirt". This fails to distinguish between the front view, back view, and close-up of the fabric.

In blogs, the common failure is keyword stuffing. Authors often paste SEO keywords into the alt field, creating unnatural, long strings. Another frequent error is using decorative images, such as blog post headers or pull quotes, without marking them as decorative. This forces screen reader users to listen to irrelevant descriptions of stock photos.

Worked Example: Auditing a Shopify Product Page

Let’s walk through a step-by-step audit of a Shopify product page for a "Men's Trail Running Shoe."

Step 1: Identify Missing Alt Text Inspect the main product image. The code shows <img src="shoe-main.jpg">. There is no alt attribute. This is a critical failure.

Step 2: Identify Generic Alt Text Inspect the thumbnail images. The code shows <img src="shoe-side.jpg" alt="image">. The alt text is generic. It does not tell the user this is a side profile view.

Step 3: Identify Keyword Stuffing Inspect the lifestyle image. The code shows <img src="shoe-lifestyle.jpg" alt="running shoes, trail running, best shoes, Nike, Adidas, cheap running shoes">. This is keyword stuffing and fails conciseness.

Step 4: Apply Fixes You need to replace these with compliant descriptions.

• Main image: alt="Men's gray and orange trail running shoe, front view"
• Side thumbnail: alt="Side profile of men's gray and orange trail running shoe"
• Lifestyle image: alt="Runner wearing gray and orange trail running shoes on a dirt path"

Step 5: Verify Decorative Elements Check the "New Arrival" badge overlay. If it is purely decorative and the text is already in the heading, mark it as decorative: <img src="badge.png" alt="">.

Automating WCAG-Compliant Alt Text Generation

For large catalogs, manual fixing is inefficient. You can use AltTextAI to generate compliant descriptions in bulk. The tool analyzes the image content to produce accurate, concise descriptions that adhere to WCAG standards.

For the Shopify example above, you would upload the product images. The system generates unique descriptions for each view, distinguishing between front, side, and lifestyle shots. It creates SEO-optimized output that naturally integrates relevant keywords to improve image search visibility.

You can then export these descriptions or use the API to push them directly to your CMS. This ensures that thousands of images are compliant without manual tagging. The key is to review a sample of the generated text to ensure it matches your brand voice, then approve the bulk update. This approach balances speed with quality, ensuring both accessibility and SEO benefits.