Alt Text SEO Best Practices: Complete Guide

Alt text is one of the most overlooked SEO opportunities on the web. Done right, it improves accessibility, boosts search rankings, and drives traffic from Google Images. This guide covers everything you need to know about alt text SEO in 2025.

What Is Alt Text and Why Does It Matter?

Alt text (alternative text) is the HTML attribute that describes what an image shows. It serves two critical purposes:

• Accessibility: Screen readers announce alt text to visually impaired users, making your content accessible to everyone
• SEO: Search engines can't "see" images - they rely on alt text to understand image content and context

When you skip alt text, you're excluding users who rely on screen readers AND missing out on valuable search traffic from Google Images.

The SEO Case for Alt Text

Google has explicitly stated that alt text is one of the most important signals for understanding images. Here's why it matters for SEO:

Image Search Rankings

Google Images is the second-largest search engine after Google itself. Alt text directly impacts your visibility in image search results, which can drive significant traffic to your site.

Page Context Signals

Alt text helps Google understand the topic and context of your entire page. Well-written alt text reinforces your target keywords and strengthens topical relevance.

User Experience Metrics

When images fail to load (slow connections, broken links), alt text displays instead. This improves user experience and reduces bounce rate - both ranking factors.

Accessibility = Legal Requirement

Beyond SEO, alt text is required by the ADA (Americans with Disabilities Act) and WCAG accessibility standards. Sites without proper alt text face legal risks.

How to Write Effective Alt Text

Writing good alt text is both an art and a science. Follow these best practices to maximize both accessibility and SEO value.

Be Descriptive and Specific

Describe what's actually in the image, not what you want it to mean. Think about what a blind user would need to know to understand the image's purpose on the page.

Keep It Concise (80-125 Characters)

Screen readers typically cut off alt text around 125 characters. Keep descriptions concise while still being descriptive.

• Aim for 80-125 characters (not words)
• Get to the point quickly
• Don't sacrifice important details for brevity
• Break very complex images into multiple images with separate alt text

Include Keywords Naturally

If your target keywords naturally fit the image description, include them. But never keyword stuff - it hurts both SEO and accessibility.

Don't Start with "Image of" or "Picture of"

Screen readers already announce that it's an image. Starting with "image of" is redundant and wastes character count.

Provide Context When Needed

The same image might need different alt text depending on the page context and purpose.

Example: Photo of a laptop on a desk

• On product page: "MacBook Pro 16-inch with M3 chip"
• On productivity blog: "Remote worker's home office setup with laptop"
• On design article: "Minimalist desk workspace with silver laptop"

Handle Decorative Images Correctly

Not all images need alt text. Decorative images (borders, spacers, pure design elements) should have empty alt attributes: alt=""

Use empty alt when:

• The image is purely decorative (background patterns, design elements)
• The information is already in surrounding text
• The image is used as a spacer or separator

Write Unique Alt Text for Each Image

Never reuse the same alt text across multiple images, even if they're similar. Each image should have a unique, specific description.

Why this matters:

• Google sees duplicate alt text as low-quality or spam
• Screen reader users get confused by identical descriptions
• Unique descriptions improve image search rankings

Common Alt Text Mistakes to Avoid

Alt Text for Different Image Types

Product Images

Include key product attributes: name, color, size, key features.

Screenshots and UI Images

Describe what interface is shown and what action it demonstrates.

Charts and Graphs

Describe the main trend or finding. Put detailed data in a table or text.

Logos

Use the company or organization name.

Infographics

Provide a brief overview in alt text, then include full text alternative nearby.

Testing Your Alt Text

Before publishing, verify your alt text works for both accessibility and SEO:

Accessibility Testing

• Read it aloud: Does it make sense when spoken?
• Use a screen reader: Test with NVDA (free) or JAWS to hear how it sounds
• Check character count: Aim for 80-125 characters
• Validate HTML: Use W3C validator to catch missing alt attributes

SEO Testing

• Google Search Console: Monitor image indexing under Coverage → Images
• Google Image Search: Search for your images to see if they rank
• SEO tools: Use Screaming Frog or Sitebulb to audit alt text at scale
• Keyword relevance: Verify alt text supports target keywords naturally

The Scale Problem: Automation

Writing perfect alt text for every image is time-consuming. If you have hundreds or thousands of images, manual alt text becomes impractical.

This is where automation helps. Modern AI can analyze images and generate descriptive, SEO-friendly alt text at scale. Learn how to bulk add alt text to WordPress images efficiently.

Alt Text SEO Checklist

Use this checklist to ensure your alt text is optimized:

1. Every informational image has alt text

   No missing alt attributes on important images

2. Alt text is descriptive and specific

   Paints a clear picture of image content

3. Length is 80-125 characters

   Concise but complete descriptions

4. Keywords are included naturally

   No keyword stuffing, just natural descriptions

5. Each image has unique alt text

   No duplicates or template text

6. Decorative images have empty alt

   Use alt="" for design elements

7. Alt text provides context

   Relevant to page topic and user intent

8. No "image of" or "picture of" prefixes

   Screen readers already announce it's an image

Frequently Asked Questions

Does alt text affect SEO rankings?

Yes. Alt text is a confirmed Google ranking factor for image search and contributes to page-level SEO by providing context. Well-optimized alt text improves both image search visibility and overall page relevance.

Should I put keywords in every alt text?

Only if they naturally fit the image description. The primary purpose of alt text is accessibility - describe what's in the image first. If your target keywords accurately describe the image, include them. Never force keywords where they don't belong.

What's the difference between alt text and image title?

Alt text is required for accessibility and SEO. It's read by screen readers and used by search engines. The title attribute (tooltip on hover) is optional and primarily for sighted users. Focus on alt text first - it's more important.

Can I automate alt text without hurting SEO?

Yes, if done correctly. Modern AI can generate high-quality, descriptive alt text that serves both accessibility and SEO. Look for tools that create unique, contextual descriptions rather than generic templates. Learn about automating WordPress alt text.

How do I audit existing images for missing alt text?

Use SEO crawling tools like Screaming Frog, Sitebulb, or your browser's inspect tool. In WordPress, go to Media → Library and check random images - if you see blank alt text fields, you have work to do.