Alt-Tag Best Practices

What are Image Alternatives?

Alt-tags (Alternative Text) are HTML attributes that provide a textual description of images. They primarily serve accessibility by helping screen readers and other assistive technologies understand the content of images. At the same time, they are an important SEO factor that helps search engines understand the context and relevance of images.

Why are Alt-Tags important for SEO?

Alt-tags play a central role in search engine optimization because they:

Improve image indexing: Search engines can better categorize and index images
Convey context: They help search engines understand the relationship between image and content
Signal keyword relevance: Optimized alt-tags can increase relevance for specific search terms
Enhance user experience: They improve accessibility and thus the overall quality of the website

Basic Alt-Tag Best Practices

1. Write descriptively and precisely

Alt-texts should describe the image precisely and objectively, without unnecessary details or marketing language.

Good:

<img src="red-apple.jpg" alt="Red apple on white background">

Bad:

<img src="red-apple.jpg" alt="The best and most delicious red apple in the world">

2. Consider context

The alt-text should reflect the context of the page and explain why the image is relevant.

Example for a blog article about healthy nutrition:

<img src="apple-slice.jpg" alt="Apple slice as a healthy snack for children">

3. Optimize length

Alt-texts should be between 5-15 words long - long enough to be descriptive, but short enough not to be overwhelming.

Optimal:

<img src="team-meeting.jpg" alt="Four-person team in conference room meeting">

4. Integrate keywords naturally

Keywords should only be used when they naturally fit into the description.

Good:

<img src="seo-Applications.jpg" alt="SEO tools dashboard with keyword analysis">

Bad:

<img src="seo-tools.jpg" alt="SEO SEO SEO Tools Keyword Research">

Special Alt-Tag Strategies

Decorative Images

Decorative images that have no informative value should receive empty alt-tags:

<img src="decorative-border.jpg" alt="">

Functional Images

Images that function as buttons or links should describe their function:

<img src="download-button.jpg" alt="Start PDF download">

Infographics and Diagrams

Complex visual content requires detailed descriptions:

<img src="seo-process-flowchart.jpg" alt="SEO process flowchart: Keyword research → Content creation → On-page optimization → Link building → Monitoring">

Avoid Common Alt-Tag Mistakes

Mistake

Problem

Correct Solution

Alt-tag completely missing

Image not recognized by screen readers

Always add alt attribute

Filename as alt-text

Not descriptive for users

Use meaningful text

"Image of..." or "Photo of..."

Redundant information

Start directly with description

Keyword stuffing

Unnatural and penalizable

Integrate keywords naturally

Too long alt-texts

Poor user experience

Use maximum 15 words

Alt-Tag Optimization for Different Image Types

Product Images

E-Commerce Optimization:

<img src="laptop-dell-xps13.jpg" alt="Dell XPS 13 Laptop in Silver with 13-inch Display">

Team Photos

People Images:

<img src="ceo-portrait.jpg" alt="Dr. Maria Schmidt, CEO of TechSolutions Company">

Screenshots

Software Demonstrations:

<img src="dashboard-screenshot.jpg" alt="Analytics Dashboard with Traffic Overview and Conversion Rates">

Diagrams and Charts

Data Visualizations:

<img src="quarterly-revenue-chart.jpg" alt="Bar chart: Q1-Q4 Revenue Development 2024, Rising Trend">

Technical Implementation

HTML Structure

<img src="image.jpg" 
     alt="Description of the image" 
     title="Additional tooltip text (optional)"
     width="800" 
     height="600">

Responsive Images

<picture>
  <source media="(min-width: 800px)" srcset="large-image.jpg">
  <source media="(min-width: 400px)" srcset="medium-image.jpg">
  <img src="small-image.jpg" alt="Description for all image sizes">
</picture>

Alt-Tag Checklist

Check before publishing:

✅ Alt attribute is present
✅ Text describes the image precisely
✅ Length between 5-15 words
✅ Keywords integrated naturally
✅ Page context considered
✅ No redundant words like "image of"
✅ Decorative images have empty alt-tags
✅ Functional images describe their function

Tools for Alt-Tag Optimization

Automatic Testing:

WAVE (Web Accessibility Evaluation Tool)
axe DevTools Browser Extension
Lighthouse Accessibility Audit

Manual Review:

Screen reader test with NVDA or JAWS
Browser developer tools for alt-tag display
SEO tools like Screaming Frog

Measuring Alt-Tag Success

KPIs for Alt-Tag Performance:

Image Indexing: Number of indexed images in Google Search Console
Image Traffic: Organic traffic via Google Images
Accessibility Score: Improvement in accessibility rating
User Engagement: Dwell time and bounce rate on image pages

Future of Alt-Tag Optimization

With the development of AI and machine learning, alt-tags will become even more important:

Automatic Image Recognition: Google can understand images better, but alt-tags remain important for context
Voice Search: Alt-tags become increasingly relevant for voice assistants
Visual Search: Optimized alt-tags improve discoverability in visual search engines