Mastering Image Optimization: SEO Expert Guidelines for Web Images

Posted on Nov. 18, 2023
Mastering Image Optimization: SEO Expert Guidelines for Web Images

Mastering Image Optimization: SEO Expert Guidelines for Web Images

One often overlooked but vital aspect of the web optimization process is image optimization. High-quality images can significantly enhance the user experience, but if not handled correctly, they can slow down your website and harm your SEO efforts. In this article, we will explore the key guidelines for image optimization, as well as some advanced tips to ensure your website's images are both visually appealing and search engine friendly.

Choose the Right File Type

Selecting the appropriate file type for your images is the first step in optimization. The two primary formats for web images are JPEG and PNG. JPEG is ideal for photographs and images with gradients, while PNG is better suited for graphics, logos, and images with transparency. Here are some suggestions to consider

Some Advanced Tips to Choose the Right File Type

  • Many people are tempted to use the least expensive TLD alternatives available when purchasing a domain name. Google's Search Relations Team, on the other hand, advises against it. Extremely cheap TLDs, particularly those available for free, frequently attract spammers, who take advantage of them to establish low-quality and spammy websites.

  • Use PNGs for simple or transparent images. PNGs can also be a good alternative to both JPEGs and GIFs.

  • Use GIFs for animated images only. You should compress your animated GIFs. Never use GIFs for large product images.

  • Logos and simple illustrations should use PNG or SVG files.

  • JPG and PNGs can also have the same quality and smaller file size with the lesser-known format, WebP.

  • WebP images are usually 25–35% smaller than JPEG and PNG images. This means that pages with WebP images will load faster for users. These are best suited for video
    However, WebP has some disadvantages, including weak browser support and poor exporting interface.

Compress Images to Reduce File Size

Image file size greatly affects page load times. This can be done by reducing the quality of the image or by finding and combining patterns within its pixels. Image compression can reduce the file size of an image by 60-70% on average. Image compression can be "lossy" or "lossless" in terms of image quality. Smaller images lead to faster load times, which is a critical SEO factor.

You can also use an online tool like TinyPNG or TinyJPG to manually compress images.

To find large size images on your website use tools like Screaming Frog.

Name Images Descriptively and in Plain Language

Image file names should be descriptive and concise. Avoid generic filenames like "image001.jpg" and instead opt for something like "white-rose-flower-bouquet.jpg." This practice not only helps with SEO but also enhances accessibility for visually impaired users who rely on screen readers.

Some advanced facts about image name:

  • Google takes note of image name in order to help figure out what the image is about.
  • If you localize your images, make sure you translate the filenames, too.
  • Changing the filename of already crawled and indexed images has the least amount of benefit to the point that it wouldn’t be visible. So, make sure to properly name at the first time.

Choose Image Dimensions and Product Angles Wisely

Consider the context in which your images will be displayed. Ensure that your images are relevant to your content and are appropriately sized. Also, provide multiple angles and views when showcasing products to give users a comprehensive understanding.

For e-commerce websites or any platform that showcases products, the selection of product angles and views can significantly impact user decision-making. Providing multiple angles and views of a product helps users make informed choices, potentially increasing conversion rates.

Resize Images to the Display Dimensions

Always resize images to the actual dimensions they will appear on your website. Displaying a large image that's scaled down by HTML or CSS slows down page loading and consumes unnecessary bandwidth.

Best Practices for Resizing Images:

  • Maintain Aspect Ratio: When resizing images, always maintain their original aspect ratio to prevent distortion. Resizing both width and height proportionally ensures that the image remains visually accurate.
  • Save in the Right Format: Depending on the content, choose the appropriate image format (JPEG, PNG, GIF) for the resized image. JPEG is typically used for photographs, while PNG is better for graphics and images with transparency.
  • Test Responsiveness: After resizing images, thoroughly test your website on various devices and screen sizes to ensure that the images adapt correctly to the display dimensions.

Use Image Sitemaps

Including image information in your sitemap can help search engines index and rank your images better. Image sitemaps provide details such as image location, title, and caption, which improve your chances of appearing in image search results.

Creating and Implementing Image Sitemaps:

  • Generate XML Image Sitemaps: To create an image sitemap, you'll need to generate an XML file that contains a list of all the images you want to be indexed. This file should include essential details for each image, such as the image URL, title, caption, and more. Many SEO plugins for popular CMS platforms like WordPress can automate this process. I usually generate image sitemaps with screaming frog.
  • Submit to Google Search Console: Once you have your image sitemap ready, submit it to Google Search Console (formerly known as Google Webmaster Tools). This tool allows you to provide Google with valuable information about your website, including your image sitemap. By doing so, you ensure that Google crawls and indexes your images more efficiently.
  • Follow XML Sitemap Guidelines: Ensure that your image sitemap adheres to the XML sitemap format guidelines. It should be structured correctly, with each image entry enclosed in the appropriate tags and containing accurate information.
  • Include Images with High SEO Value: While it's a good practice to include all your website's images in the sitemap, prioritize images that have high SEO value. These could be images of your products, infographics, or any visuals directly related to your content.

Use a Content Delivery Network (CDN)

A CDN distributes your website's content across multiple servers worldwide, reducing server load and improving page load times. This is especially crucial for image-heavy websites as it ensures fast image delivery to users regardless of their location.

Implement Lazy Loading

Lazy loading is a technique that defers the loading of images until they are visible on the user's screen. This reduces the initial page load time and improves the overall user experience.

Here is how to do it: <img src="image.jpg" alt="Description" loading="lazy">

Monitor your website's performance using tools like Google PageSpeed Insights to measure the improvements in page load times.

Leverage Browser Caching

Utilize browser caching to instruct a user's browser to store images locally. This means that when a visitor returns to your website, their browser can retrieve cached images instead of re-downloading them, further reducing load times.
Add Cache-Control and Expires Headers in your .htaccess file

Correctly Sequence Image Downloads

Optimize the order in which images are loaded on your webpage. Prioritize important content-related images over decorative ones to ensure that users see essential visual elements first.

Insights: The Data That Paves Your Path

Ah, data, the navigator of your digital ship! Delve into Google Business Profile insights and unearth what's clicking. Are folks resonating with your posts? What are they on the hunt for? This treasure trove empowers you to tweak your strategies and surge ahead.

Add Descriptive Alt Text

Alt text provides a textual description of an image, aiding users who cannot view images and assisting search engines in understanding image content. Ensure your alt text is descriptive and relevant to the image.

Some interesting facts about alt text:

  • A logo that functions as a home page link should contain alt text that tells a screen reader user that the logo is a homepage link.

  • Sometimes a link is in the form of an icon, with no text to explain what it does. The best practice is to describe what the image does (initiate an email or print a webpage).

  • Similar to the example of the icon, the alt text for a button image should describe what the image does.

  • Do not use redundant alt text for example; alt text of a screenshot say that the image is a screenshot or an image is an image is annoying.

  • But if you’re just adding alt text for the first time, then sometimes, even any alt text is better than nothing. Then you can improve on that later.

  • Add alt text to decorative images also because these are unique and special image. Something like “floral background”

Use Relevant Images that Match Your Text

Images should complement your content, providing context or visual aids to your text. Avoid using irrelevant or generic images that do not enhance the user's understanding of your content.

Use Captions Appropriately

For images that benefit from additional context or clarification, consider adding captions. Captions make it easier for users to scan your page and understand the image's significance.

Utilize Image Alt Text and srcset

For responsive design, use the srcset attribute to serve different image sizes to various screen resolutions. This ensures that users on different devices receive appropriately sized images, improving load times and user experience.

srcset can be implemented as follows:

  • Include the srcset Attribute in Your HTML: <img src="image.jpg" alt="Description" srcset="image-400.jpg 400w, image-800.jpg 800w, image-1200.jpg 1200w">

  • Specify Image Sizes (Optional): <img src="image.jpg" alt="Description" srcset="image-400.jpg 400w, image-800.jpg 800w, image-1200.jpg 1200w" sizes="(max-width: 600px) 100vw, (max-width: 1000px) 50vw, 33.3vw">

Image Structured Data


  • Improved SEO: Image structured data enhances the visibility of your images in search results, potentially leading to higher organic traffic.

  • Better User Experience: Rich image results provide users with more information at a glance, making it easier for them to find relevant content.

  • Enhanced Mobile Experience: As mobile devices become the primary means of internet access, structured data helps optimize image presentation on smaller screens.

Types of Image Structured Data:

There are various types of image structured data that you can use, including:

  • ImageObject: This type provides information about a specific image, including its URL, width, height, and caption.
  • ImageGallery: Useful for websites with galleries or albums, this type allows you to group related images together.

  • Product Image: If you have an e-commerce site, you can use structured data to describe product images, including details like price and availability.

  • Logo: This type is used to mark up your site's logo, providing details such as the URL and image dimensions.

  • Breadcrumb: Although not specific to images, structured data can also be used for breadcrumb navigation, making it easier for search engines to understand the site's structure.

Google changes the requirements for image structured data to make it easy to add credit, creator and copyright information

AI Images on Websites

Apparently the use of AI images within a website is okay. According Google’s John Muller if the image is really cool and unique.