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Alt Attributes for Images: Best Practices for SEO

John Koinange

John Koinange is a digital marketing associate and regular contributor for the Lockedown SEO blog. His work has appeared in numerous online publications.

Alt text—also known as alternative description, alt tags, or the alt attribute, is the written text accompanying in an image on a web page that is read by screen readers.

The alt tag is an attribute of the img tag in HTML. While the alt attribute is not required, it is highly recommended for accessibility purposes.

The text helps visually impaired users understand the image on your web page, and may be considered a characteristic of a high quality web page by Google’s ranking algorithm.

This is an example of how the alt attribute appears in an img tag in HTML.



<img src="image.jpg" alt="image description" title="image tooltip"> 


The src attribute is the file path to the image. The alt attribute is the alternative text that screen readers read on assistive browsers. The title attribute is the text that appears in tooltips when a mouse hovers over the image.

When an image is delayed in loading, or fails to load, the alt attribute text may be visible in a web page where the image should be located.

Here is a video that explains some best practices for alt attribute text.

Why Should You Add Alt Attribute Text?

It’s imperative to optimize the alt attribute text on your website whether you perform SEO or not, as this creates a better user experience for people visiting the site. Adding alt text to images encourages people to read your content, boosts the authority of the message, improves organic traffic and ranking in the image search results.

Google’s Quality Rater Guidelines state,

“For all types of webpages, creating high quality MC [main content] takes a significant amount of at least one of the following: time, effort, expertise, and talent/skill.”

Though it does not explicitly state here that adding text to the alt attribute on all image tags is a sign of high page quality, anecdotal evidence suggests that this is the case.

Contextual images that strengthen the content of the page should also contain alt text to make the website easily accessible. Summarily, the alt text describes what’s on an image and its purpose on a page.

Defining Image Attributes

Consider at the following HTML image tag.



<img src="image.jpg" alt="image description" title="image tooltip"> 


While alt and title image attributes are often referred to as alt tags and title text, they are not tags but attributes of the img tag. The alt text defines the utility of an image (description and purpose). It’s the alt attribute that enables visually impaired screen users to decipher the context by reading it. The title attribute, while not required, shows a tooltip when users hover over an image element with a mouse.

Every image should contain alt text not only for SEO purposes but also for easy accessibility. Visually impaired individuals won’t know the contents of the image; hence a title tag is not necessary. It’s applicable for people using a mouse or other pointing devices.

A title tag is not required for an HTML image to render. However, if the title tag relays relevant information with keywords, integrate the information in plain text or somewhere else.

*If an image doesn’t serve any purpose but purely exists for design purposes, the image should be in the CSS rather than the HTML of your website. In WordPress, leave the field marked “Alternative text” empty, located in the Image Settings.

Recommended Practices for Alt Attributes

Here is an example of recommended alt text in HTML.



<img src="puppy-playing.jpg" alt="Adorable puppy playing catch" /> 


The alt text is inside the alt ="" attribute of the img tag.

The example highlights the need to choose a proper file name while using images. Google seeks to understand the purpose of an image without looking at it. Attaining this goal requires one to name the image file using focus keyphrases relevant to the content.

Avoid keyword stuffing as this affects user experience and exposes your site to a spam label. Instead, describe what is happening in the image as simply as possible.

Alt Text, Images and SEO

Google’s guidelines on best practices for images instruct ‘use descriptive alt text’ for images in a web page. This speaks volumes on the value of alt attribute text. Google applies alt text to determine the image content and its context within the content displayed.

Loading speed is an integral element for SEO and user experience (UX). Images highly affect the loading speed. It is advisable to use resized images without compromising on the image quality. Larger images affect loading speed hence slowing down the responsiveness of your site.

Google keeps getting better at recognizing images though it’s advisable to use images within your content that are closest to the related content. The utility of an image to both users and Google depends on the message relevance surrounding it. Also, use images sparingly and within an optimized website.

Structured Data and Images

Integrating structured data – describing a website to make it easier for search engines to understand – boosts the chances for your content to be designated as rich results by the search engines. Google says structured data doesn’t improve ranking but aids in helping the algorithm understand the listing in the image results.

Read more about Google’s policy on Structured Data Guidelines here.

SEO for Images: Best Practices Checklist

  • Use relevant alt attribute text on all images
  • Make sure your alt text describes the image, and is not simply keyword-stuffed
  • Pick an appropriate file name for the image
  • Ensure image size and image dimensions match
  • Reduce the image size to enhance faster loading
  • Add appropriate image captions when appropriate for added context
  • Title attribute text in images is not required, but provides tooltip text on mouse hover
  • Where possible, add structured data to the image
  • Optimize context for all your images. An image should add context to the main content of a web page.

More Questions on SEO?

If you have more SEO questions, contact Lockedown SEO for guidance on how to rank higher in organic Google search results.

John Koinange

John Koinange is a digital marketing associate and regular contributor for the Lockedown SEO blog. His work has appeared in numerous online publications.

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