The general best practice for alt text is under 125 characters, with WCAG suggesting under 100 characters as a guideline. Screen readers like JAWS handle approximately 125 characters well. Key best practices: be descriptive, include your keyword naturally (once), don’t start with “Image of,” and use empty alt (alt="") for decorative images. The primary purpose is accessibility for screen reader users, with SEO benefits as a secondary consideration.

This guide covers alt text best practices that prioritize accessibility while supporting your search optimization goals.

Alt Text Length Guidelines

Recommended Character Limits

What Actually Matters

Screen reader behavior:

• Modern screen readers don’t strictly truncate alt text
• Users can pause, navigate, and re-read alt text
• JAWS handles approximately 125 characters well
• Overly long descriptions can be tedious, not impossible

Practical guidance:

• Simple images: 10-50 characters
• Standard images: 50-125 characters
• Complex images: Consider extended description elsewhere
• Charts/infographics: Brief alt text + detailed caption or data table

Alt Text Purposes

Accessibility (Primary Purpose)

Who uses alt text:

• People using screen readers
• People with slow internet connections (images don’t load)
• People who’ve disabled images
• People with cognitive differences benefiting from descriptions

What screen readers do:

• Read alt text aloud when encountering images
• Allow navigation between images
• Provide context for understanding page content

Accessibility statistic: WebAIM’s 2024 analysis found 54.5% of homepages have images missing alt text—a significant accessibility failure.

SEO (Secondary Purpose)

How Google uses alt text:

• Understands image content for image search
• Provides context for surrounding content
• Helps index images appropriately

SEO best practices:

• Include relevant keywords naturally
• Describe what’s actually in the image
• Don’t keyword stuff

User Experience

When images fail to load:

• Alt text displays in place of the image
• Provides context even without the visual
• Maintains page understandability

Writing Effective Alt Text

Best Practices

Do:

• Be descriptive
• Include keyword naturally (once)
• Keep under 125 characters as a general rule

Don’t:

• Start with “Image of” or “Picture of” (screen readers announce it’s an image)
• Keyword stuff
• Add excessive detail unrelated to content purpose

The Basic Framework

Include:

1. What the image shows (primary subject)
2. Relevant context (why it’s there)
3. Action or relationship (if applicable)

For decorative images:

• Use empty alt (alt="") to tell screen readers to skip the image

Examples by Image Type

Product image:

• Weak: “Shoe”
• Better: “Red Nike running shoe, side view”
• Best: “Red Nike Air Max 90 running shoe, side view showing air unit”

Person/portrait:

• Weak: “Woman”
• Better: “Woman smiling at camera”
• Best: “Marketing director Sarah Chen speaking at conference podium”

Screenshot:

• Weak: “Screenshot”
• Better: “Screenshot of settings page”
• Best: “Gmail settings page showing the ‘General’ tab with signature options highlighted”

Chart/graph:

• Weak: “Graph”
• Better: “Bar chart showing sales data”
• Best: “Bar chart showing quarterly sales growth from $2M to $3.5M over 2025”

Decorative image:

• Correct: alt="" (empty alt attribute)
• Why: Decorative images shouldn’t be announced by screen readers

When to Use Empty Alt Text

Decorative Images

Definition: Images that add visual appeal but no information

Examples:

• Background textures
• Decorative dividers
• Purely aesthetic elements
• Icons adjacent to text that says the same thing

Implementation: <img src="decoration.jpg" alt="">

Why empty, not missing:

• Missing alt attribute = accessibility error
• Empty alt attribute = intentionally decorative
• Screen readers skip images with empty alt

Icons with Adjacent Text

Example: A phone icon next to “Call us: 555-1234”

Alt text: Empty (alt="") because the text already conveys the meaning

If icon alone: Needs alt text like “Phone” or “Call us”

Alt Text for Complex Images

Charts and Graphs

Challenge: Visual data is information-dense

Approach options:

1. Brief alt text summarizing the main takeaway
2. Detailed description in surrounding text
3. Data table as alternative
4. Link to long description

Example: Alt: “Line graph showing website traffic doubled from January to December 2025” Surrounding text: “As shown in the graph, traffic grew from 50,000 monthly visitors to 100,000…”

Infographics

Challenge: Too complex for alt text alone

Best practice:

• Alt text summarizes topic: “Infographic explaining the coffee brewing process in 6 steps”
• Full text version available elsewhere on page or linked
• Consider whether infographic is truly necessary

Screenshots with Text

Challenge: Text in images isn’t readable by screen readers

Approach:

• Alt text describes what the screenshot shows
• If text in image is important, include it or link to it
• Consider whether a screenshot is necessary

Alt Text and SEO

How Google Uses Alt Text

Image search:

• Alt text helps images appear in Google Images
• Relevant keywords improve discoverability

Page context:

• Alt text provides additional context about page content
• Can reinforce topical relevance

Keyword Integration

Do:

• Include relevant keywords where natural
• Describe what’s actually in the image
• Prioritize accuracy over keyword inclusion

Don’t:

• Stuff keywords unnaturally
• Use alt text solely for SEO
• Describe things not in the image

Example:

• Good: “Barista preparing latte art in coffee shop” (if about coffee shop content)
• Bad: “Best coffee shop Seattle latte art barista cheap coffee beans” (keyword stuffing)

Alt Text Checklist

Before Publishing, Verify:

• Every informational image has alt text
• Decorative images have empty alt attributes (alt="")
• Alt text describes what’s in the image accurately
• No “image of” or “picture of” prefixes
• Length matches image complexity (10-250 characters)
• Keywords included naturally where relevant
• Complex images have additional text descriptions nearby
• Icons with adjacent text have empty alt attributes

Common Alt Text Mistakes

Missing Alt Attributes Entirely

Problem: <img src="photo.jpg">

Impact: Major accessibility failure; screen readers may read file name

Fix: Always include alt attribute, even if empty for decorative images

“Image of…” Prefix

Problem: alt=“Image of a sunset over mountains”

Why it’s wrong: Screen readers already announce “image,” making it redundant

Fix: alt=“Sunset over mountain range with orange and purple sky”

File Names as Alt Text

Problem: alt=“IMG_4582.jpg” or alt=“hero-banner-v2-final.png”

Impact: Meaningless to screen reader users

Fix: Write actual descriptions

Keyword Stuffing

Problem: alt=“best running shoes cheap running shoes buy running shoes online Nike running shoes”

Impact: Bad for accessibility and SEO (Google penalizes this)

Fix: Natural description with one relevant keyword if applicable

Identical Alt Text for Different Images

Problem: Every product image has alt=“Product image”

Impact: Unhelpful for users navigating between images

Fix: Unique, descriptive alt text for each image

Frequently Asked Questions

Is there a maximum alt text length?

No official maximum, but keep alt text as concise as possible while being descriptive. Screen readers will read it all, so respect users’ time.

Should all images have alt text?

All images need an alt attribute. Informational images need descriptive text. Decorative images should have empty alt (alt="").

Do background images need alt text?

CSS background images can’t have alt text. If the image conveys important information, use an <img> tag instead or provide the information in text.

How does alt text affect SEO?

Alt text helps Google understand images for image search and page context. Natural keyword inclusion can help, but accuracy matters more than keywords.

Should I include my brand name in alt text?

Only if relevant. For logo images, yes: alt=“Company Name logo”. For product photos, focus on describing the product.

What about captions vs. alt text?

Captions are visible to everyone; alt text is for screen readers. They serve different purposes and can complement each other.

Key Takeaways

• General best practice: under 125 characters
• WCAG suggestion: under 100 characters
• Screen reader (JAWS): handles ~125 characters well
• Be descriptive and include keyword naturally (once)
• Don’t start with “Image of” or “Picture of”
• Use empty alt (alt="") for decorative images

Conclusion

Alt text is fundamentally an accessibility feature—write it for people using screen readers first, then consider SEO benefits. The myth of strict length limits persists, but the reality is simpler: be descriptive, be accurate, and be concise. Every informational image deserves alt text that helps users understand what they can’t see. Try our free letter counter → to check your alt text length while crafting image descriptions.