What is Image Alt tag and Is It Important for SEO?

One of the most common SEO mistakes I see on websites is the absence of alt tags on images. Many webmasters underestimate the importance of the image alt tag because they don’t fully understand its role in SEO.

In this article, I’ll explain the function of the image alt tag in SEO and why it’s essential to use it properly on your website.

What is Image Alt Tag?

The alt tag, short for “alternative text,” is an image-specific attribute added to the HTML tag of an image (or the <img> tag). It is visible in the source code of the page but not on the page itself.

The purpose of the alt attribute is to provide an alternative text description of an image.

According to the W3C (World Wide Web Consortium):

The alt text specifies an alternate text for user agents that cannot display images.
— W3C

What is it used for?

Website visitors can see and interpret images simply by looking at them, so they don’t need the alt tag to understand the image’s content. However, there are several cases where users may rely on the alt text to understand what an image represents:

• Users who have disabled images in their browsers: Some people prefer to disable images in their browsers to make web pages load faster. In this case, visitors can’t see the image but can read the alt text to get an idea of what the image depicts.

• Users with slow internet connections: If someone has a slow internet connection, images may not load, but they can still access the information in the alt tag.

• Users with visual impairments: People who use screen readers to navigate the web rely on the alt text to understand the content of images. The alt text is read aloud by the screen reader, making the web more accessible to visually impaired individuals.

• Search engine crawlers: Search engines like Googlebot and Bingbot can’t “see” images. Instead, they rely on the alt text to understand what the image is about and how it relates to the rest of the page content.

Why is the Image Alt Tag important for SEO?

The image alt tag plays a vital role in SEO. In a 2007 video, Google’s Matt Cutts emphasized the importance of alt text when Google tries to understand what an image is about. He stated that:

… providing useful, accurate information in your ALT attributes can make your photos and pictures more discoverable on the web.

Matt Cutts also mentioned that the alt attribute is “very useful for Google” and that it’s enough for search engines to “know what’s going on in an image.”

By using the alt tag properly, you help search engines gather more context about your webpage’s main topic and keywords. Think of the alt tag as an opportunity to improve the relevance of your webpage for your targeted keywords.

How to write SEO-optimized Image Alt tags?

Now that you understand why image alt tags are important for SEO, here are some tips on how to write effective and SEO-optimized alt text:

1. Include Keywords: The alt text should describe the image clearly and concisely while incorporating the main keyword or keyword phrase of the page. If the targeted keyword doesn’t directly align with the image, consider using a different image that better fits the topic and keyword.
2. Length: Aim for a length of around 10–15 words. Alt text that is too long can negatively affect the user experience, especially for users who have disabled images in their browsers.
3. Descriptive and Keyword-Rich: You can either write a full sentence or a short, descriptive text. The key is to include relevant keywords while making sure the description accurately reflects the image.

Why the absence of image Alt tags is an SEO mistake?

Failing to include an image alt tag is a common SEO mistake for several reasons:

• You miss providing search engines with valuable information about your images.
• You lose a valuable keyword opportunity to enhance your page’s relevance.
• You provide a poor user experience for visitors who have disabled images in their browsers.

 This is why SEO audit tools often flag missing or duplicate alt tags. Such issues can negatively impact your website’s SEO performance and may even be considered a signal of poor website quality by search engines like Google.

Many SEO guides emphasize the importance of the image alt tag as a key on-page SEO element. If you’re not using alt tags correctly, you’re missing out on an important aspect of SEO optimization.

10 Frequently Asked Questions (FAQs) About Image Alt Tags

What is the purpose of an image alt tag?

The image alt tag provides a text description of an image, helping search engines understand its content and improving accessibility for users with disabilities or slow internet connections.

How does the image alt tag affect SEO?

The alt tag helps search engines index and rank images, improving visibility in image search results and contributing to the overall SEO performance of a webpage.

What should I include in an image alt tag?

Your alt text should briefly describe the image and include relevant keywords. It should be descriptive and provide context, ensuring it aligns with the page’s content.

How long should an image alt tag be?

Aim for 10-15 words. This length is optimal for conveying the image’s purpose without overwhelming users or search engines.

Can I use the same alt tag for multiple images?

Each image should have a unique alt tag that accurately describes it. Using duplicate alt text can confuse search engines and lead to SEO issues.

Are image alt tags important for mobile SEO?

Yes! Image alt tags improve accessibility and help search engines understand image content, which is important for mobile-first indexing and optimizing your site for mobile users.

Can alt tags be used for SEO if the image is decorative?

If the image is purely decorative and doesn’t add value to the page, you can leave the alt attribute empty (alt=””). This tells search engines and screen readers to ignore the image.

Is there a limit to how many keywords I should include in my alt tag?

Avoid keyword stuffing. Focus on writing natural, descriptive alt text that fits the context of the image, using keywords only when appropriate.

Do image alt tags affect image search rankings?

Yes, properly optimized alt tags can help your images appear in image search results, increasing visibility and traffic to your website.

Can I use the alt tag to rank for multiple keywords?

While it’s important to include relevant keywords, it’s better to focus on one primary keyword per image to avoid overloading the alt text and ensure it remains natural and descriptive.

Conclusion

The image alt tag is a small but significant component of SEO. Not only does it improve accessibility for users with visual impairments or slow internet connections, but it also helps search engines understand the context of your images, which can improve your rankings in search results. By writing descriptive, keyword-rich alt text, you can make your images more discoverable, boost your SEO efforts, and enhance the overall user experience on your website.