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Guide to Image Optimization for SEO, Site Experience, and Accessibility

Dec 07, 2022   |   SEO
Guide to Image Optimization for SEO, Site Experience, and Accessibility

By Erik Newton, VP of Marketing at Milestone Inc.

People like images. They engage more with posts and articles with visuals applicable to the text. As you develop content for your website, including pictures across your pages can give your material a valuable boost. 

However, not only can images encourage people to pay attention to what you have to say, but optimizing those images can help you appeal more to the search engines and impact your SEO. Image optimization or SEO is more complex than adding alt text to every picture you upload. Instead, you need to consider what image it is carefully and its role on your site to help you maximize the SEO potential.  

Here is some data about images and SEO: 

  1. About 22% of SERPs contain images (Milestone). 
  1. CTR on images goes from 0% to 9% with an average of just under 2% blended mobile and desktop (Milestone). 
  1. As you do better with image impressions, you will see a decline in average Google search traffic conversion (paid search looks like it converts better but is about the same once adjusted for organic images.) (AJ Kohn). 

We will break down what you need to know about optimizing images for your site and properly using alt text. 

What value do images offer? 

What value do images offer?

Before we break down how to optimize images on a website, it is important to explore the value that images bring to your page. Think of images as entities within the greater entity of your website. Each image brings its own opportunities to add keywords to alt-text and page text, increase engagement, earn SERP rankings through images searches, and to employ schema. 

Given the diverse roles that images can play within a website, brands should prioritize creating original images. Stock photos are not unique to your brand and thus offer your website little value. They will not apply directly to your products or services and therefore do not contribute much to the points you make. Customers may also encounter the same images on other websites which will detract from your brand’s reputation. Original images reflect the human side of your brand, which also plays well in our modern age of personalization.  

As you develop your original visuals, you can stitch them together as well to build web stories.  

Google Web Stories allow you to select particular images that you want to have played in sequence. When you publish a Web Story, customers can click and have each image load for them automatically, creating an immersive experience. You can even include elements like quizzes in the sequence to encourage engagement with customers. 

Web Stories can be an important part of building a brand story on your website. Use the images to express the core ideas of your brand, communicating to customers why they should listen to your organization over others in the industry. You can read more about effective storytelling with your website here

Of course, incorporating images into your website will not be a band aid solution that immediately creates a highly effective, engaging site. Instead, it is one component among many that will build a desirable digital experience that will connect well with site visitors and therefore encourage conversions. Our research at Milestone has found that about 22% of SERPs contain images. Having these images can increase your brand impressions, but it will not necessarily build a large CTR for you. Image results CTRs typically hover between 0 and 9%, and the traffic that comes through images doesn’t convert as well as the traffic that comes from other sources.  

Instead, look at images as an important component in adding a personal touch to your textual content. They draw in user interest, encourage people to take interest in what you have to say, and can increase your impressions on the SERPs. 

Why do you need to optimize your images? 

Alt text on your page has two main functions: 


The first job is increasing the accessibility of your site. Alt text explains what the visuals on your site represent since screen readers cannot ‘see’ the image itself. This text allows people with visual disabilities to engage fully with your page.  

It is this accessibility feature that makes it important to use alt text when on visuals such as logos or buttons. John Mueller of Google says that using alt text on these ‘functional’ images does not contribute to SEO, but it does contribute to the accessibility of your site. For example, you might note if a logo also serves as a button that will take people back to your main page. Even if it does not directly help to boost your rankings, it provides a better user experience for all people who land on your site, which will be a net positive for your business.  


The second purpose of alt text is optimization. Like the site reader, algorithms cannot ‘see’ your image, so using alt text helps the site crawlers better grasp how the visuals contribute to your overall site value.  

Why focus on image SEO? 

What is image SEO?

Search has evolved and so must your SEO strategy. On one hand, Google has focused on improving the experience offered to customers on websites, such as the Thin Content, Smith, and Page Experience algorithm updates. On the other hand, and here’s where it gets super interesting, the BERT, MUM, LAMDA and PaLM algorithms are now focusing on entities within content to derive the most relevant answer to a query. Yes, keyword-driven SEO is more a thing of the past and semantic or meaning SEO is what all businesses and brands need to lean in on. It’s not just entities within content on a webpage that are being picked out, but for voice commands, videos, and even images – basically multi-search.  

Now think about this, open your laptop or mobile and take a look at what’s occupying the significant above-the-fold SERP space. It’s images. Whether it’s a product inventory, menu items from a restaurant, or even movies or actors, image SERP results have grown exponentially over the last few years.  

So the big question? How is Google picking out these images for a certain query? The answer is simple. It’s mapping entities to images and those relevant images are getting displayed for a relevant query. Which means, foundationally you’ve got to start optimizing each image that you publish as an entity.   

Step 1: The first step is to remove duplicates. The approach that Milestone takes with its Asset Library is to use the same image across locations, channels, and devices. This creates an entity out of the image once optimized. Every image is reused across locations and channels and automatically rendered for different devices.  

Step 2: You’ve got to recognize the entities within an image. Milestone’s vision data component automatically detects all entities within an image. For example, whether it’s a building by the sea, it has a walking path around the bay, there are streetlamps, and so on. Each of those entities that have being recognized get tied to the image. The image is then automatically marked up with image schema for entity recognition.  

Step 3: Quality check of the images is a must. Poor quality will just depreciate your SEO efforts. Carry out a quality check of the images and publish only those that meet the standards. The image then needs to be an accepted and adaptable format (WebP, PNG, JPEG, BMP, GIF, and SVG) and rendered effectively for different devices to ensure it meets the page experience requirements with loading, interactivity, etc.  

Step 4: Addition of meta details and alt text. This approach will not only help with efficient management of images – internal search of the images, but will better describe the image to search engines. Alt text and meta details will basically offer more context of an image. After all, keep in mind that people look for context within an image and whether it matches their query before clicking on it.  


A large component of image SEO targets the alt text you develop to help search engines understand your pictures and images so that the crawlers know what the visuals contribute to your page. The text you create should focus on the function of the image for your website. Ask yourself if the image provides informational value, offers a particular function– such as a button, or if it’s purely decorative and does not contribute much to the user. You do not need to prioritize the alt text for images that do not offer value for the page experience. As you create your alt text, focus on providing context for the image and its value.  

John Mueller offers this example

“So if you have a picture of a beach, don’t just be like, ‘Oh, this is a photo of a beach.’ But rather like, ‘This is the beach before the chemical spill happened.’” 

This type of context clearly articulates the value of the image and the context in which users will find the image important. Not only will it help site visitors using site readers understand where the picture fits in with the rest of your page, but it also can help your image show up in image searches. 

As you develop the text for the image, you also want to pay attention to how you write. Do not waste time and words with phrasing like, “this is an image of…” or “this is a screenshot of…” 

Instead, go straight to the highly relevant words that articulate what the picture shows. Saying ‘image’ or ‘screenshot’ at the start of the alt text becomes unnecessary and redundant. 

Incorporating image schema 

As you add images to your page, you also have the opportunity to provide more information about the visual through schema markup. When using schema, you can mark an image as either an ImageObject value or URL value.  

With the ImageObject value, you can provide the search engines with more information about the image, such as the size of the item or a description of the image. The more information you can provide through the schema, the easier it will be for Google to know when to display your image properly and the value the image offers visitors to your page, further boosting your image SEO. 

Formatting the image properly 

Formatting the image properly for Image SEO

Google has made it clear that when it comes to rankings, speed matters tremendously. Therefore, the formatting of your images will have an immediate impact on the overall SEO of your page. Customers do not like slow-loading web pages, so the search engine does not either. As you add visual elements to your site, optimize them for speed.  

Google specifically mentions WebP formats for images. This format creates a smaller file size that allows pages to load faster without using poor-quality images. Other image formats that can appear in Google Images include WebP, PNG, JPEG, BMP, GIF, and SVG. You also want the images to be responsive so that customers have a positive experience on your page regardless of the size screen they employ. 

How to make sure your images have been properly optimized? 

As you optimize the image on your site, you will want to follow these best practices to get the most out of the process. 

  1. Determine the purpose of the image on your site. Is this a decoration, something that adds value, or a functional picture? 
  1. Decide what format you will use for your image, selecting the option that will maximize your speed without sacrificing quality. 
  1. Determine the goal for your alt text. Is this alt text purely for site readers to help people navigate the site or to boost your image optimization? 
  1. What is the context of the image? If you were describing your page to someone, what would you say about why you picked this particular image? 
  1. Write your alt text. Now, create a direct, descriptive line about your image. Do not use unnecessary words but instead focus on articulating the picture’s context and value. 
  1. Include image schema to give the search engines all the relevant information about the image. 
  1. Be sure to optimize the file size and keep most below 100k. 
  1. Adding relevant words to the file name is a good practice that helps internal administrators is a fallback signal when no other on-page information is available to the search bot. 

What is image optimization and why is it important for SEO?

Image optimization is the process of improving the performance and accessibility of images on a website in order to improve the user experience and increase the chances of ranking well in search engine results. Image optimization is important for SEO because it can help improve the user experience, speed, and engagement of a website, which are factors that can impact search engine rankings.

How can I optimize my images for SEO?

There are a few key steps you can take to optimize your images for SEO:

  • Use descriptive, relevant file names for your images
  • Compress your images to reduce their file size without sacrificing quality
  • Use alt text to describe the content and context of your images
  • Use responsive images to ensure that your images display correctly on different devices
  • Use structured data to provide additional context and information about your images to search engines

Can I use any image file format for SEO?

Not all image file formats are created equal when it comes to SEO. Some image file formats, such as JPEG and PNG and WebP, are more widely supported and tend to be better suited for use on the web. Other image file formats, like GIF and BMP, may not be as widely supported and may not be the best choice for use on a website.

Is it better to use images or videos for SEO?

Both images and videos can be effective for SEO, but it ultimately depends on the content and context of your website. If you have visual content that is well-suited to being displayed as an image, then using images may be the better choice. On the other hand, if you have visual content that is better suited to being displayed as a video, like entertaining, funny, or surprising content, then using videos may be the better choice.

How can I ensure that my images are accessible to all users?

Ensuring that your images are accessible to all users is important for SEO and for providing a good user experience. Some steps you can take to make your images more accessible include:

  • Using alt text to describe the content and context of your images
  • Providing transcripts or captions for any audio or video content
  • Using structured data to provide additional context and information about your images to search engines
  • Ensuring that your images are properly formatted and have adequate contrast
  • Using responsive images to ensure that your images display correctly on different devices

Get more out of your website 

Your website is your business’s home on the web. Not only can it help customers learn more about your business and what you have to offer, but it can also attract more leads. With SEO best practices, like understanding the intricacies of image SEO, you can develop a site that will rank well and find new customers. 

If you are ready to take your site to the next level, reach out to us at Milestone. We can help you create more than just a website; we will help you build a digital experience for your customers. 

Contact our expert team at [email protected] or call us at 408-200-2211 to learn more about Milestone’s image solutions. 

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