Alt Text: Why It's Important For Accessibility & SEO - Moz

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1. SEO Learning Center
2. On-Site SEO
3. How To Write the Best Alternative Text

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How To Write the Best Alternative Text

Updated by Chima Mmeje — March 24, 2025.

What is alternative text?

Alt text, or alternative text, is a short description added to images on a webpage. It helps improve web accessibility and optimize for search engines. Alt attributes play a crucial role in enhancing both accessibility and SEO. For users who rely on screen readers, alt text provides crucial context about images, making web content more inclusive. At the same time, search engines use alt text to understand image content, which can contribute to better rankings in image search results. The alt tag is essential in making digital content more accessible, especially for visually impaired users.

For website owners, content creators, and digital marketers, alt text allows you to create accessible, search-friendly content. Whether you’re optimizing an article, an e-commerce product page, or a social media post, writing clear and effective alt text ensures your images are meaningful to all users.

Alt text helps visually impaired users by providing descriptions that screen readers can relay. Additionally, search engines analyze alt text to determine image relevance, which can boost a webpage’s SEO performance. By including appropriate alt text, you make content more accessible and improve its visibility in search results.

Alt text example

Here’s an example of an alt text:

The alt text for this cute image is “Golden retriever puppy playing with a red ball on grass”

A bad example of an alt text would be “Dog” or “Picture of a cute dog.”

The first alt text demonstrates the importance of writing concise alt text that is descriptive yet brief. This ensures that anyone reading understands what the image is about. Additionally, alt text is crucial when an image fails to load, ensuring users still receive context about what the image depicts.

Fix your alt text with Moz Pro Campaigns

Optimize my alt text

Why is alt text important?

Alt text enhances both accessibility and SEO. Screen readers interpret alt text to provide meaningful descriptions of images to visually impaired users. The primary goal is to serve visitors with different abilities while also improving image search rankings. Additionally, alt text plays a critical role in search engine optimization (SEO) by making visual content more discoverable and understandable by search engines.

Key benefits of alt text include:

Improve accessibility for users with visual impairment and screen readers

Alt text enables screen readers to describe images for users with visual impairments, low vision, and different learning abilities. Understanding the impact of alt text becomes clear when considering these statistics that SEO expert Miracle Inameti-Archibong during her MozCon presentation:

• 12 million internet users have a visual impairment or low vision.
• 83% of people with accessibility needs prefer sites that meet accessibility standards, even if prices are higher.
• 97.4% of homepages have accessibility errors, with missing alt text accounting for 61% of these errors.
• In 2021, there were 10 lawsuits per day in the US related to website accessibility.

For decorative images, using an empty alt attribute (alt=””) tells screen readers to ignore the image, improving the experience for visually impaired users.

Ensuring proper alt text implementation makes your website more inclusive while reducing legal risks and maximizing engagement. Non-informative images can negatively impact a screen reader user’s experience by increasing reading time and causing confusion.

Provide context for image searches

Alt text helps search engines like Google categorize and rank images on a webpage. Proper alt text on a web page aids accessibility, particularly for users with visual impairments, and enhances SEO by providing descriptive text alternatives for images. When queries benefit from visual results, image packs appear prominently in search.

While Google uses computer vision technology to analyze images, alt text remains vital for providing context that algorithms alone may not fully capture.

Improve user experience and increase image traffic

Alt text improves usability for all users, especially those with slow internet connections where images may not load properly. Alt tags (alternative text) not only substitute for images that fail to load but also assist search engines in understanding content, increasing your website’s visibility in search results, and driving more traffic to your site. 

Surfacing images in search results, whether in Google Images or as image packs, attracts thousands of additional visitors. Hence, writing optimized alt text is a win-win for both accessibility and SEO.

Alt text best practices (rules and guidelines)

Writing optimized alt text requires a balance between clarity, conciseness, and relevance. Follow these best practices to ensure accessibility and SEO best practice:

Be descriptive but concise

Keep alt text under 125 characters while forming a clear mental image of the content.

Focus on purpose, not just appearance

Describe what the image conveys rather than listing visual details.

Avoid unnecessary phrases

Skip “image of” or “picture of”—screen readers already indicate that it’s an image.

Use keywords naturally

Incorporate relevant keywords without stuffing; align with user search intent.

Handle decorative images properly

For purely decorative images, use an empty alt attribute (alt=””) so screen readers can ignore them.

Complex images need extra context

For maps, charts, and infographics, follow W3C Web Accessibility Initiative guidelines and provide a full explanation in surrounding text or linked descriptions.

Alt text for buttons

Ensure buttons using images (e.g., “submit” or “sign up”) have clear alt text describing their function.

Use CSS for purely decorative images

Keep decorative elements out of HTML and manage them via CSS to avoid unnecessary alt text.

Fix your alt text with Moz Pro Campaigns

Optimize my alt text

How to write alt text for different image types

Different images require unique approaches when writing alt text. Use these guidelines to write effective descriptions:

Logos

Describe the brand and purpose (e.g., “Moz logo – SEO software”).

Charts and graphs

Summarize key data insights instead of describing visual elements.

Icons and buttons

Explain the function (e.g., “Search button” or “Download PDF”).

People

Include actions, expressions, or relevant identifiers when necessary.

Decorative images

Use alt=”” so screen readers ignore them

Common alt text mistakes to avoid

Writing effective alt text requires avoiding common mistakes that can reduce accessibility and hurt SEO. Here are some frequent pitfalls and how to correct them:

Being too vague

Using file names or generic terms (e.g., "Image1234.jpg").

Over-explaining

Adding unnecessary phrases like "This is an image of...".

Keyword stuffing

Overloading with keywords (e.g., "SEO, SEO strategy, SEO tools image").

Neglecting important images

Failing to add alt text for images that convey essential information.

How to add alt text to images in a CMS

Many content management systems will have options to add and edit alt text when you’re uploading your content. 

Adding alt attributes is crucial for both accessibility and SEO, as it helps screen readers and search engines understand image content better. Follow these steps for different systems:

WordPress

When uploading an image, locate the “Alt Text” field in the media library and enter your description.

Shopify

In the product editor, click on the image, select “Edit Image” and enter the alt text in the provided field.

Wix

Click on the image, select “Settings,” and type the alt text in the “What’s in the image?” field.

Squarespace

Open the image editor, find the “Image Metadata” section, and add your alt text in the “Alt” field.

Weebly

Click on the image, choose “Advanced,” and enter the alt text under “Alternative Text.

How to check alt text with Moz

With MozBar, you can view your alt text directly from your browser. On the left side of MozBar, click Page Analysis, select On-Page Elements, and scroll down to view all alternative texts for the page.

You can also view other on-page elements like metadata, titles, subheadings and more.

Alternatively, head over to Campaigns in Moz Pro to see issues hurting on-page SEO and suggestions to fix them. You can find this information in Moz Pro - Campaigns - Page Optimization

Enter your website URL and the primary keyword for the page. When the result populates, scroll down to view issues hurting on-page SEO like using keywords in alt-text.

You'll also receive some instructions on how to fix the specific issues, alongside some content suggestions to help the page rank higher in SERPs and improve your online visibility.

Conclusion: Use alt text to improve accessibility and SEO

Alt text is a simple yet powerful tool that enhances web accessibility and helps search engines understand your images. By following best practices, you ensure that your content is inclusive, user-friendly, and optimized for search visibility.

Get a comprehensive list of your page alt text

with Moz Bar

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Frequently asked questions about alt text

What is the optimal alt text format?

The best format for alt text is sufficiently descriptive without unnecessary keyword stuffing. A good test is to have someone read the alt text aloud—if they can visualize the image accurately, the alt text is effective.

How long can alt text be and is there a limit for decorative images?

According to Google, there is no strict character limit for alt text. Instead, focus on writing alt text that is descriptive but not overly long. Google's John Mueller has confirmed that there are no specific guidelines on length, so use common sense to describe the image thoroughly but concisely.

Is alt text a ranking factor?

Yes, alt text is a ranking factor for Google Image Search. According to Google's John Mueller, alt text helps Google understand and rank images. While alt text is treated like other on-page text for general search, it is a major search ranking factor.

What is the difference between alt text and image description?

Alt text is a short, concise description embedded in the HTML alt attribute for accessibility and SEO. An image description, on the other hand, is a more detailed explanation typically displayed on the page, providing more context and details about the image for all users.

Get a comprehensive list of your page alt text

with Moz Bar

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