Alt Attributes in SEO: A Complete Guide

Alt attributes—often referred to as “alt tags” or “alt text”—are a fundamental component of web accessibility and search engine optimisation (SEO); specifically on-page SEO. While they may appear simple, they play a critical role in providing descriptive alt text alternatives to images. This helps not only screen readers and users with visual impairments but also search engines like Google to interpret and index visual content accurately.

In this guide, we will explore what alt attributes are, why they matter for SEO and accessibility, and how to write proper alt text to improve your website’s visibility in image search results.

What Are Alt Attributes?

Alt attributes (commonly called alt text or alt tags) are a piece of HTML code added to image elements on a webpage. The primary purpose is to describe the content and function of an image when the image cannot be displayed or for users who rely on assistive technologies such as screen readers.

Here’s a basic example of how an alt attribute appears in HTML:

<img src="golden-retriever-puppy.jpg" alt="Golden retriever puppy playing in a garden">

In this example, the alt text provides context about what the image shows. This is helpful both for SEO purposes and for improving accessibility.

Benefits of Alt Attributes

Alt attributes, also known as alt text, offer a multitude of benefits for website owners, digital marketers, and users alike. Here are some key advantages:

• Improved Accessibility: Alt text enables screen readers to describe images to visually impaired users, making it easier for them to navigate and understand web pages. This is crucial for creating an inclusive online experience.
• Enhanced SEO: Alt text helps search engines like Google understand the content of images, which can improve image search rankings and drive more traffic to a website. Optimised alt text can significantly boost your site’s visibility in search results.
• Increased User Engagement: By providing a clear and concise description of an image, alt text helps users understand the context and purpose of the image, leading to increased engagement and a better user experience.
• Better Image Indexing: Alt text assists search engines in indexing images correctly, making it easier for users to find relevant images in search results. This can enhance your site’s overall search engine performance.
• Improved Website Usability: Alt text provides a fallback for images that fail to load, ensuring that users still receive context about the image. This maintains the flow of information and prevents gaps in the user experience.

By leveraging these benefits, you can create a more accessible, engaging, and SEO-friendly website.

The Bridge Between Images and Understanding

Alt text refers to the actual content within the alt attribute. It tells users—and search engines—what the image conveys. Descriptive alt text is essential for providing context when images fail to load, ensuring users understand the content. If an image fails to load due to network issues or other reasons, the browser displays this alt text in its place. This makes it easier for users to understand what they’re missing.

Screen readers use this descriptive text to narrate the content of an image to visually impaired users. Therefore, writing alt text that is concise, relevant, and informative is vital for both usability and inclusivity.

Alt Tag: Misnomer or Still Relevant?

Though often called the “alt tag,” this is technically incorrect. The alt attribute is not a tag itself but rather part of an HTML <img> tag. However, due to common usage in the SEO and web development community, the term “alt tag” is widely understood to mean the alt attribute or the alt text.

Image Alt Text: Why It Matters

Image alt text is crucial for several reasons:

1. Improves accessibility – Helps users who rely on a screen reader to understand visual content.
2. Supports SEO strategy – Enables search engines like Google to understand and index your images.
3. Enhances user experience – Provides context when an image cannot be displayed.
4. Increases visibility – Can lead to more traffic from image search results such as Google Images.

A Signal for Search Engines

The image alt attribute serves as an important SEO signal. Search engines are not yet able to interpret images with 100% accuracy, though computer vision algorithms are improving. This makes image alt attributes essential for helping search engines determine how an image relates to the surrounding content.

For example, if your WordPress website includes a blog post titled “10 Tips for Training a Golden Retriever,” and you include an image with the alt attribute “Golden retriever puppy sitting with a treat,” this provides context and reinforces the topic.

Google Images and Image Search Results

A well-written alt text can help your website’s images appear in Google Images and other image search results. This additional exposure can bring in more traffic from users searching for relevant visual content.

Google often includes image packs in standard search results, especially for queries with a visual component. Proper SEO alt text increases the likelihood that your images are included in these results.

Alt Text Best Practices

Effective alt text is both an art and a science. Here are the key alt text best practices:

• Be descriptive but concise: Summarise what the image shows in under 125 characters.
• Use keywords appropriately: Include relevant keywords, but avoid keyword stuffing.
• Avoid filling alt attributes with unnecessary or repetitive phrases.
• Don’t use “image of” or “picture of”: Screen readers already identify the element as an image.
• Provide context: Explain how the image relates to the page content.
• Leave alt attribute empty for purely decorative images (e.g., alt=””).
• Use descriptive alt text to provide detailed and accurate descriptions of images.

Common Alt Text Mistakes to Avoid

When writing alt text, it’s essential to avoid common mistakes that can reduce accessibility and hurt SEO. Here are some pitfalls to watch out for:

• Being Too Vague: Alt text should be descriptive and concise, providing a clear understanding of the image content. Avoid generic descriptions like “image” or “photo.”
• Using File Names or Generic Terms: Alt text should be specific and relevant to the image content, rather than using generic terms or file names. For example, instead of “IMG_1234.jpg,” use “Golden retriever puppy playing in the garden.”
• Over-Explaining: Alt text should be brief and to the point, avoiding unnecessary details or descriptions. Aim for clarity without verbosity.
• Adding Unnecessary Phrases: Phrases like “This is an image of…” or “Picture of…” are redundant and can make alt text less effective. Screen readers already identify the element as an image.
• Keyword Stuffing: Alt text should be written for users, not just for search engines. Avoid stuffing alt text with keywords, and focus on providing a clear and concise description.
• Neglecting Important Images: All images on a web page should have alt text, including decorative images, logos, and icons. Even if an image seems minor, providing alt text ensures comprehensive accessibility and SEO.

By avoiding these common mistakes, you can ensure your alt text is effective, user-friendly, and SEO-optimised.

Image Description: What Makes It Work?

A proper alt text or image description provides enough detail for a user to understand the purpose of the image without being overly verbose.

For example:

• Poor: “Dog”
• Better: “Golden retriever puppy”
• Best: “Golden retriever puppy sitting on a green lawn with a red ball”

The third example provides context, descriptive text alternatives, and helps search engines and screen readers understand what the image conveys.

Decorative Images: When to Use an Empty Alt Attribute

Some images are used purely for visual design and do not add to the content or meaning. These should use an empty alt attribute (alt=””) so that screen readers skip them. This avoids cluttering the user experience for visually impaired users.

Examples of decorative images:

• Background flourishes
• Borders or shadows
• Icons that are repeated and not meaningful on their own

By marking these images correctly, you improve accessibility and reduce the chance of creating a negative user experience.

Add Alt Text in Your CMS or Site Builder

Most content management systems, such as WordPress, make it easy to add alt text via the media library or block tab. When adding images to your post or page, you will typically find an “Alt Text” field where you can type in your description.

In WordPress, for instance:

1. Upload an image to the media library.
2. Click on the image to open its settings.
3. Find the Alt Text box and enter your descriptive text.
4. Save and insert the image into your content.

This applies whether you’re building a site from scratch or managing an extensive digital content archive.

Add Alt: A Small Step With Big Impact

Don’t overlook the importance of taking the time to add alt text to your images. It’s one of the simplest, most effective ways to make your content more usable and findable. Whether you’re optimising for SEO, enhancing user experience, or meeting accessibility standards, alt attributes deserve your attention.

Improve Accessibility and SEO Together

A well-optimised SEO strategy considers technical SEO, content quality, and accessibility. By ensuring that each image includes optimised alt text, you’re supporting:

• Better performance in search engines
• Enhanced usability for all users, including those using a screen reader
• Compliance with accessibility guidelines
• A more robust and information rich content structure across your web pages

Incorporating proper alt text is particularly valuable in the era of AI-driven computer vision algorithms, where Google uses both image data and text to determine rankings.

Tools and Resources

There are several tools and resources available to help website owners and digital marketers optimise their alt text and improve accessibility. Here are some of the most popular options:

• Moz Pro Site Crawl: This tool helps identify and fix missing alt text on a website, ensuring all images are properly described.
• Yoast SEO: A popular plugin that provides a feature to check if the key phrase is in the alt attributes, helping you optimise your alt text for SEO.
• AI Alt Text Generator: This tool generates alt text for images in over 130 languages, making it easier to create descriptive and inclusive alt text.
• WordPress Plugin: Automatically generates alt text for every new image added to the media library, saving time and ensuring consistency.
• Browser Extensions: Extensions like the AltText.ai Chrome Extension and Firefox AddOn allow users to right-click on any image and get alt text to copy and paste, simplifying the process of adding alt text.
• Automations: Pre-built connectors for Zapier, Pabbly, Albato, and SureTriggers allow users to build a fully automated alt text generation workflow, streamlining the process of optimising alt text.

By using these tools and resources, website owners and digital marketers can ensure that their alt text is optimised, accessible, and provides a better user experience for all users.

Example: Writing Effective Alt Text

Let’s say you’re publishing an article about dog training and you include a photo with the filename golden-retriever.jpg.

Here’s how you might approach the alt text:

• Filename: golden-retriever.jpg
• Alt Text: “Golden retriever puppy sitting attentively during obedience training”

This alt text includes:

• A descriptive phrase
• A relevant keyword
• Specific context
• No filler words or unnecessary detail

Final Thoughts

Alt attributes are far more than just an SEO checkbox. They’re a powerful tool that bridges the gap between visual content and accessible, meaningful web experiences. From increasing visibility on Google Images to supporting users who rely on screen readers, taking the time to craft effective alt text is a crucial step in building a successful, inclusive website.

Whether you’re managing a WordPress website, publishing content for your business, or optimising your site for technical SEO, always remember to:

• Write proper alt text
• Add alt attributes to all meaningful images
• Leave decorative images with empty alt attributes
• Use keywords appropriately
• Prioritise clarity, accuracy, and relevance

By following these practices, you not only comply with accessibility standards but also improve your website’s chances of being discovered by the right users through image and web search.

For best results, review your existing images and make sure they include useful, descriptive, and SEO-friendly alt text. It’s a small detail that can lead to big gains in usability and organic traffic.