How to write alt text for SEO: Best practices

Jun 12, 2024 | SEO

If you’ve ever added an image to a website, you may know the term “alt text” and that it has implications for SEO, or search engine optimization. But what exactly is the purpose of this text and how do you write it?

Images are essential for creating engaging web content. They break up text, illustrate points, and enhance the overall user experience. However, not all of your website users are able to view your images, whether due to a visual impairment or the occasional technical issue. This is where alt text comes in.

Aside from accessibility, alt text is also beneficial for SEO because of keywords. In this post, we’ll cover the alt text best practices for improving both SEO and accessibility.

What is alt text and why is it important?

Alt text, short for alternative text, is a written description of an image that appears in place of the image if it fails to load. It’s also read by screen readers to describe images to visually impaired users.

Although there is no character limit for alt text, it’s typically no more than one sentence long. For most images, a brief description (say, around 100 characters) should be sufficient to describe the image contents. For complex images, like charts or infographics, a longer description may be necessary.

Alt text is important for accessibility

For visually impaired users, alt text provides essential context, allowing them to understand the content and purpose of images on a webpage. This makes your content more inclusive and accessible to a broader audience.

Click here to learn more about website accessibility and why it’s important.

Alt text is important for SEO

Search engines use alt text to index and understand the content of images. This helps improve your website’s search rankings, as images with descriptive alt text are more likely to appear in image search results, driving additional traffic to your site.

Alt text is a great place to add your target keywords for the page. In general, pages containing images with keywords in the alt text will have a higher likelihood of ranking for the keywords than pages without any images.

Alt Text Best Practices

Be Descriptive

Your alt text should accurately describe the content and function of the image. Instead of generic terms, use specific language to convey what the image depicts. For instance, instead of “cat,” you might write “gray cat lounging on a windowsill.”

Be Specific and Concise

While it’s important to be descriptive, you should also keep your alt text concise. Aim for around 125 characters or fewer, as some screen readers may cut off longer descriptions.

Avoid Keyword Stuffing

Including relevant keywords in your alt text can help with SEO, but overloading it with keywords (known as keyword stuffing) can harm your search rankings and readability. Focus on creating natural, descriptive text.

Contextual Relevance

Ensure your alt text is relevant to the surrounding content. This helps users and search engines understand how the image relates to the page’s overall topic. For example, if you have an article about baking, an image of a chocolate cake might have alt text like “freshly baked chocolate cake with frosting.”

Common Alt Text Mistakes to Avoid

Writing alt text is pretty straightforward. However, there are a few common mistakes that are worth knowing and correcting.

Using “Image of…” or “Picture of…”

Starting your alt text with phrases like “image of” or “picture of” is redundant. Screen readers already announce that an image is present, so it’s unnecessary to include this information.

Leaving Alt Text Blank

Leaving alt text blank might be acceptable for purely decorative images that don’t add meaningful content. However, for any image that conveys important information or context, always provide a descriptive alt text.

Using Alt Text for Decorative Images

For images that are purely decorative and do not add content, it’s better to use a null alt attribute (alt=””) so that screen readers skip these images, allowing users to focus on the essential content.


Writing effective alt text is an essential skill for enhancing both accessibility and SEO. By being descriptive, specific, and relevant, you can ensure your images are accessible to all users and optimized for search engines. Now is a great time to audit your current alt text and implement these best practices.

Additional Resources

For further reading on SEO and accessibility, check out these authoritative sources:

For a beginner-friendly deep dive into SEO, including keyword research, content writing, link-building and more, check out my course, the SEO Essentials Kit.

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