What Is Image Alt Text?
Alt text (alternative text) is an HTML attribute that describes the content of an image. It serves two critical purposes:
- Accessibility — Screen readers read alt text aloud to visually impaired users
- SEO — Search engines can't "see" images; they rely on alt text to understand what an image shows
<img src="seo-dashboard.png" alt="SEO audit dashboard showing a score of 85 with 3 errors and 8 warnings" />
Why Alt Text Matters
Search Engine Image Understanding
Google Images is the second largest search engine. Without alt text, your images are invisible to it. Descriptive alt text helps your images appear in image search results, driving additional traffic.
Accessibility Compliance
Alt text is required by WCAG (Web Content Accessibility Guidelines). Sites without proper alt text may face legal compliance issues and exclude users who rely on assistive technology.
Fallback When Images Don't Load
When an image fails to load (slow connection, broken URL), the alt text displays in its place, preserving the meaning of the content.
Context for Search Engines
Alt text provides additional context about the surrounding content, reinforcing the page's topical relevance.
Common Alt Text Issues
| Issue | Impact |
|---|---|
| Missing alt attribute | Images invisible to search engines and screen readers |
| Empty alt text on meaningful images | Lost SEO opportunity, poor accessibility |
| Generic alt text ("image", "photo") | No useful information for anyone |
| Keyword-stuffed alt text | Can be flagged as spam |
| Alt text on decorative images | Adds noise for screen reader users |
How to Write Good Alt Text
1. Be Descriptive and Specific
Describe what the image actually shows, not what you want it to rank for.
Bad: SEO SEO audit tool SEO checker
Good: Bar chart comparing page load times across mobile and desktop
2. Keep It Concise
Aim for 125 characters or fewer. Screen readers may truncate longer text.
3. Don't Start With "Image of" or "Photo of"
Screen readers already announce that the element is an image. Starting with "image of" is redundant.
4. Include Keywords Naturally
If the image genuinely relates to your target keyword, include it naturally — but never force it.
5. Use Empty Alt for Decorative Images
Purely decorative images (borders, spacers, icons) should have empty alt attributes (alt="") so screen readers skip them.
Checking Alt Text Across Your Site
Manually auditing alt text on every image is tedious. An automated audit should:
- Flag images with missing alt attributes — highest priority
- Detect generic alt text — "image", "photo", "untitled"
- Find overly long alt text — over 125 characters
- Identify keyword-stuffed alt text — unnatural repetition
- Report image file sizes — large unoptimized images hurt performance
Kaitico scans every image on every page during an audit, reporting missing and problematic alt text alongside the image URL and page location.