Image optimisation for SEO: How To Optimise Images

Image optimisation for SEO is one of the most underused strategies. Images make your content more accessible, attractive and engaging to users. If you optimise images for SEO, your images to display more prominently in image SERP results can help your website pull in more traffic whether you're focused on local SEO or international SEO - and thus potentially increase your leads.

But don't just take our word for it, here is a quote from Rand Fishkin (Founder of SparkToro and Co-founder of Moz) , an authoritative figure in the world of SEO:

"Optimising images is crucial for maintaining fast load times. If your images are too large, it can severely impact your page speed and thus your SEO." Moz Blog

There are many areas of image optimisation that need to be actioned to ensure you correctly optimise images for SEO, below we look at providing some tips and image SEO best practices that need to be considered when uploading new images onto your website.

Table of Contents

• Image File Names
• Image Format
• Image Sizing
• Responsive Images
• Image Loading
• Image Compression
• ALT Text
• Image Captions
• Image Titles
• Structured Data
• Image Sitemaps
• Image Optimisations FAQs

Prioritise High-Quality Content That Meets User Needs

Before we get to tips on image optimisation for seo, the first consideration is choosing the actual images themselves.

Images make your website visually appealing, breaking up large chunks of text and make your content more digestible. A well-designed layout with relevant images can grab the attention of visitors and keep them engaged.

This will help your SEO as Google tracks user behavior metrics like time spent on a page and bounce rates. Therefore, well-chosen images that keep users on your site longer, are sending positive signals to search engines that your content is valuable.

You will need to choose a relevant, and ideally, unique image to be used on the page or blog post. Using your own unique custom imagery is often the best option. However, if you don't have your own Images, feel free to use stock images. They are fine to use, however, if other websites have used them before, you may find getting it to rank highly in image results difficult. Just make sure when using stock images that you have the right permissions as it is important to avoid potential copyright infringements, as you dont want to find yourself in the middle of a lawsuit for using a copyrighted image!

USE AI Tools

AI is transforming image creation and recognition, helping generate relevant images that support SEO objectives. AI-powered image recognition enables search engines to better understand and index images, improving visibility and user engagement. This results in better rankings, as AI makes it easier for search engines to categorise visual content accurately, ensuring it appears in the most relevant search results. This image optimisation for seo not only enhances accessibility but also increases click-through rates, ultimately benefiting SEO efforts.

Choose the right image file name for image optimisation for SEO

Before we get into the best way to name images for SEO, it's important to understand why naming your images properly has an impact on SEO.

When search engines like Google crawl your site, they can't "see" images the way humans do. Instead, they rely on file names, alt text, and surrounding content to understand what the image is about. Therefore, properly naming your images can help SEO for several reasons:

Improve Search Engine Indexing

Adding descriptive alt text for images helps search engines understand and categorise your images accurately. This ensures that your visuals are properly indexed, making them more discoverable online. Well-structured alt text contributes to better search visibility and relevance.

Increase Visibility in Google Image Search

Optimised alt text improves the likelihood of your images appearing in Google Image Search results. This can drive more organic traffic to your website through visual search. Using relevant keywords within alt text enhances search rankings without keyword stuffing.

Boost Overall SEO Performance

Well-written alt text strengthens your page’s SEO by making content more relevant and accessible. Search engines consider alt text when determining page quality, which can positively impact rankings. Proper image optimisation contributes to a better-structured and more search-friendly website.

Enhance Accessibility for Users with Disabilities

Alt text provides essential context for users who rely on screen readers to navigate web content. Descriptive alt tags make visual elements more accessible, improving the browsing experience for visually impaired users. Ensuring inclusivity in web design benefits both accessibility and overall usability.

How to name image files for SEO

When choosing the right Image file name for SEO you’ll want to make it as easy for Google to know what the image is about without even looking at it, so naming image files for SEO using your focus keyphrase in the image file name can let you tell them what it is from the file name.

For instance, when naming your images, use descriptive file names that include relevant keywords. This helps search engines understand what the image is about and match it to relevant search queries. For example, instead of naming an image IMG_12345.jpg, name it something like yorkshire-tea-factory-tour.jpg. as that is the best way to name images for image optimisation for SEO.

Choose the right format

Each image format has different properties, such as file size, compression quality, and browser compatibility, which can influence how efficiently your website loads and how well it ranks in search results. Depending on the image and how you want to use it, there are different file formats that should be considered.

Most commonly there are 3 types of Image formats which can be used:

JPEG for larger photos or illustrations as the colours and clarity will be kept in smaller files.

PNG for background and large images - if you want to preserve background transparency in your image

SVG for logos and icons as they can be resized without any loss of image quality

Google recommends using next-gen image formats like WebP for better compression and faster load times. These formats can significantly reduce file sizes without sacrificing image quality, which improves both speed and SEO performance.

How to convert image formats for SEO

You can convert existing images (like JPEG or PNG) to WebP using image editing software, online converters, or even code-based tools. You can create WebP images using different tools like online converters. Below is a guide on converting an image to WebP and then uploading it to your website.

Step 1: Choose an Online Converter

Start by selecting an online converter, such as CloudConvert or Convertio, to convert your image to WebP format. These websites offer easy-to-use tools for image conversion.

Step 2: Upload Your Image

Next, upload the image (JPEG, PNG, etc.) that you wish to convert from your computer. Follow the prompts on the converter website to select your image file.

Step 3: Convert to WebP

Select WebP as the desired output format and begin the conversion process. The website will automatically compress and convert your image to WebP.

Step 4: Download the WebP Image

After the conversion is complete, download the WebP image file to your computer. Make sure to save it in an easily accessible location.

Step 5: Log in to WordPress

Log in to your WordPress dashboard to start adding the WebP image to your site.

Step 6: Upload Your WebP Image

Navigate to Media > Add New, and either drag and drop your WebP image into the upload area or click "Select Files" to browse for it.

Step 7: Insert the Image

Once the upload is complete, you can insert the WebP image into your posts or pages, just like any other image. Simply select the image and add it to your content.

Image sizing

Using the correct image size is crucial for optimizing page load times and improving the overall user experience. If an image is uploaded at a larger size than needed, such as 1500x750 pixels but displayed as 150x75 pixels, the larger file is still loaded, which unnecessarily slows down the page. By ensuring that the image size matches the display size, you can reduce the load time, enhance site performance, and prevent potential bounce rates due to slow loading.

Use responsive images

Responsive images are ideal for image optimisation for SEO as they automatically adjust their size based on the device’s screen size, resolution, and orientation. This means that images will look sharp and load efficiently on any device, whether it's a smartphone, tablet, or desktop computer. Better user experience leads to lower bounce rates, higher engagement, and increased time spent on your site—all positive signals for SEO.

Depending on how your website is built, you may need to ensure that your images are responsive so that they load correctly on mobile and desktop devices alike.

The good news is that, If you are using the WordPress CMS, this is done automatically for you, however, if you are not, you will need to add the ‘srcset’ attribute to your image’s CSS code.

Best Practices for Responsive Images

Always test how images appear on various devices and screen sizes to ensure they look good and perform well. Testing how images appear across various devices and screen sizes is a critical step in the image optimisation process. This practice ensures that your images not only look good but also perform well, regardless of the device used to access your website.

Most modern browsers come with built-in developer tools that allow you to simulate various devices and screen sizes. For example, In Chrome, press F12 or right-click and select Inspect. Then click the Toggle Device Toolbar icon to test different devices and screen resolutions. This will alow you to view how images are shown on different devices.

Lazy Loading

Lazy loading is a technique where images are only loaded when they are about to enter the viewport, meaning they are visible to the user as they scroll down the page. This improves page load times by reducing the number of images that need to be loaded initially, which enhances user experience and reduces bounce rates. From an SEO perspective, lazy loading helps improve page speed—a crucial ranking factor—and ensures that images are optimised for faster rendering, ultimately benefiting search engine visibility and rankings.

Image Compression for image optimisation for SEO

To ensure that you optimise images for SEO correctly, we would recommend that you look at your file sizes.

Image compression is the process of reducing the file size of an image while maintaining as much visual quality as possible. This is achieved by eliminating redundant or unnecessary data. Compression helps in reducing storage space, improving load times on websites, and optimising images for various applications. There are 2 options for this, firstly you can upload the image in the correct size and thus a much smaller file image or you can use a compression tool.

Types of compression

There are many 2 compression options for image optimisation - Lossless and lossy compression.

Lossless Compression

Lossless compression is a method of reducing an image’s file size without sacrificing quality. Unlike lossy compression, which permanently removes some image data to achieve smaller sizes, lossless techniques retain all the original information, allowing the image to be perfectly reconstructed. This makes lossless compression ideal for applications where image accuracy is essential, such as medical imaging, technical drawings, and graphic design. By eliminating redundant data rather than discarding image details, it ensures that no visual quality is lost while still reducing storage space and improving efficiency.

Several compression methods are commonly used in lossless image formats. Techniques such as Run-Length Encoding (RLE) compress images by identifying and simplifying repeated sequences of pixels, while Huffman Coding assigns shorter binary codes to frequently occurring data for more efficient storage. The PNG format, one of the most widely used lossless image formats, relies on DEFLATE compression to reduce file size without losing quality. Other formats, such as GIF and BMP, also use lossless techniques to preserve image integrity. These formats are particularly useful for images with sharp contrasts, transparency, or text elements, where maintaining precise detail is crucial.

Lossy Compression

Lossy compression is a technique used to reduce the file size of an image by permanently discarding some of its data. This method significantly decreases storage requirements and improves loading speeds, making it ideal for web usage, social media, and digital photography. By removing less noticeable details, lossy compression achieves higher compression ratios compared to lossless methods, though repeated compression or excessive reduction can lead to visible artefacts such as blurring or pixelation.

Several image formats utilise lossy compression, with JPEG being the most common, balancing quality and file size efficiently. WebP and HEIF are modern alternatives that offer improved compression efficiency while maintaining better visual fidelity. Lossy compression techniques, such as Discrete Cosine Transform (DCT) and wavelet-based methods, optimise image storage by prioritising the most important visual details while reducing redundant or imperceptible data. While this approach is effective for general images, it may not be suitable for detailed graphics, medical imaging, or professional photography where accuracy is crucial.

Image Compression Tools

Onsite Images - There are many compression tool options for image optimisation of images already uploaded, including WPSmush, ImageOptim, Gimp or Squoosh. You can set these to run audits periodically to ensure that all your images - new and old - are compressed at all times, helping with load speeds.

Images Pre-loading - Should you have images that are yet to be uploaded onsite, there are many image compressions tools available to you to compress before they get uploaded. If you are looking for offline tools, the better programs are Adobe Photoshop, GIMP and ImageOptim (Mac-users only). If you are looking for online programs, you should look at tinypng.com, squoosh.app or optimizilla.com.

The Benefits of image optimisation for seo

Image compression plays a crucial role in enhancing website performance, particularly in terms of search engine optimisation (SEO). 

Load Speeds

One of the key benefits is faster loading times. Search engines like Google prioritise websites that load quickly, as page speed is a significant ranking factor. Compressed images reduce the overall page size, leading to quicker load times, improved user engagement, and lower bounce rates—all of which contribute to better SEO performance.

Reduced Server Requirements

In addition to speed, image compression helps reduce storage and bandwidth costs. Large image files take up considerable space on servers and require more bandwidth to load, especially on websites with high traffic. By compressing images, businesses can lower their hosting expenses and ensure their content loads efficiently, even for users with slower internet connections.

UX

A seamless user experience is another important factor in image optimisation for SEO, and compressed images help achieve this by ensuring smooth performance on both mobile and desktop devices. As mobile browsing continues to dominate, optimising images for quick loading and responsiveness is essential for retaining visitors and improving search rankings.

Display Better

Finally, efficient image compression allows for better transmission and storage in digital applications. Whether for e-commerce, online publishing, or social media, optimised images load faster and display correctly across various platforms. This not only enhances user satisfaction but also aligns with best SEO practices, helping businesses maintain a competitive edge online.

Image Alt Text for image optimisation for SEO

The image alt tag (or ALT text) serves multiple important purposes. It provides a descriptive text alternative for images when they can't be displayed, ensuring accessibility for visually impaired users. Additionally, alt tags are valuable for SEO, offering an opportunity to include relevant keywords or key phrases for the page, which can help improve search engine rankings. However, it’s essential to ensure the alt text is both descriptive and relevant to the image, while avoiding keyword stuffing.

Image alt tags SEO best practices

As an example, the alt text for the image yorkshire-tea-factory-tour.jpg could be: “A guided tour of the Yorkshire Tea factory showing the production process.” This will work well as the alt text adds context for search engines and improves accessibility, contributing to better SEO performance.

Keep It Concise

Aim for alt text that is concise and effective, limiting it to 125 characters or fewer. This ensures that the description is easy to understand and doesn't overwhelm the user. Shorter alt text is also better for search engine optimisation.

Avoid "Image of" or "Picture of" Phrases

Skip using redundant phrases like "image of" or "picture of," as they don't add value. Instead, focus on going straight to the description of the image. This keeps the alt text clear and more accessible.

Use Alt Tags for All Important Images

Make sure to add alt text to all content-related images, including product photos and infographics. This is essential for accessibility and ensures users can fully engage with the visual content. Alt tags help improve SEO as well.

Make Alt Text Unique for Each Image

Even if images are similar, each should have unique alt text to avoid duplication. Unique descriptions provide more context for each image, improving accessibility and search engine ranking. Avoid generic alt text to ensure each image stands out.

Focus on Accessibility

When writing alt text, always consider users who rely on screen readers. Effective alt text provides these users with meaningful descriptions of visual content. This improves the overall accessibility of your website or digital platform.

Optimise Alt Text for Image Search

Optimise your alt text by using relevant, keyword-rich descriptions to improve image search ranking. Well-optimised alt text can help images appear in search results, driving more traffic to your site. Keywords should be naturally integrated without stuffing.

Optimise Alt Text for Image Search

Periodically audit and update your alt text to keep it aligned with current SEO best practices. Over time, images and content may change, and alt text should reflect this. Regular updates ensure that the alt text remains relevant and effective for both accessibility and SEO.

How to edit Image Alt Text

Editing Image Alt text can be done when uploading a new image to WordPress, or can be added to existing Images which are saved in WordPress media Library. Here’s how you can do it:

Step 1: Go to Media Library

From your WordPress dashboard, navigate to Media and then select Library. This will take you to a page displaying all your uploaded images.

Step 2: Find and Select the Image

Scroll through your library or use the search function to find the image you wish to edit. Click on the image to open its details.

Step 3: Edit Alt Text

In the Attachment Details panel on the right side, locate the Alt Text field. Add or modify the alt text in this field to provide a clear description of the image.

Step 4: Update Image

After editing the alt text, click the Update button to save your changes. This will ensure your alt text is applied to the image.

Captions

The image caption is the text that usually accompanies the image on the page in a box underneath the images. According to Kissmetrics in a 2012 survey, captions are read on average 300% more than the body copy itself, so this is a vital opportunity that needs to be used to hook in potential readers.

Image Title Text

Title text appears when your mouse hovers over the image. Most people will simply copy the ALT tag to use as this title text, which is fine to do, however, we would recommend using a unique description of the image for the title.

Utilise image-structured data

Adding structured data, such as image schema markup, enhances how Google and other search engines interpret and display images in search results. While it doesn't directly impact rankings, structured data improves visibility by enabling richer image results, which can increase click-through rates (CTR) by providing more detailed, relevant listings. By offering more context to images, schema markup helps search engines understand the content better, which can lead to improved engagement and more visibility in image searches.

XML image sitemaps for image optimisation for SEO

An image sitemap provides a structured list of your website’s images, making it easier for search engines like Google to discover and understand them. Creating an image sitemap in WordPress can significantly enhance your SEO by helping search engines index your images more effectively.

In fact, Google themselves say it is a good idea to “use Google image extensions for sitemaps to give Google more information about the images available on your pages. Image sitemap information helps Google discover images that we might not otherwise find”, so with this in mind, it would be foolish to exclude your image files from sitemaps when considering image optimisation for SEO.

How you can create an image sitemap

One of the easiest ways to create an image sitemap is by using a WordPress plugin. Here’s how to do it:

Install Yoast SEO as your Sitemap Plugin
Navigate to Plugins > Add New in the WordPress dashboard. Search for Yoast SEO, then install and activate the plugin.

Enable Image Sitemaps
Go to SEO > General > Features in the dashboard. Make sure the XML Sitemaps option is enabled.

Access the Sitemap Settings
Click the question mark icon next to the XML Sitemaps setting to open the sitemap settings.View the Image Sitemap
Click the See the XML Sitemap link, then add ?sitemap=image to the end of the URL in the browser's address bar. This will allow you to view the image sitemap.

Creating an image sitemap is a straightforward process with the help of plugins like Yoast SEO. By improving image indexing, providing context, and enhancing visibility, an image sitemap can play a significant role in driving traffic and optimising your website’s performance.

FINAL THOUGHTS

"Image optimisation is essential for SEO. Properly optimised images improve page load times, enhance user experience, and help with higher search rankings."

Neil Patel (Neil Patel Blog)

As you can see, there are many actions & tips to take away so you can ensure that your images are optimised on your website. Keep these 10 things below in mind when adding an image to an article and you should find your images helping your overall SERPs performance:

1. Use relevant images for your page copy

2. Pick a good, relevant, file name for your image

3. Make sure you upload an image with the image dimensions that match the size displayed

4. Use ‘srcset’ if necessary

5. Reduce file size for faster loading

6. Add a caption, using keywords if appropriate

7. Use image alt tags

8. Add structured data to your images

9. Add images in your XML sitemaps

10. Provide all the context you can to help not only Google but also your website users

How can We help you With Your image optimisation for SEO

Our Technical SEO service in Leeds can help you understand how your images are currently performing and how you can further optimise images for SEO to ensure optimum performance. Contact us to discuss how our image optimisation service could help you conquer your targeted search results.

Image Optimisation for SEO FAQs

How do ACtion image optimisation for SEO?

To optimise images for SEO, start by reducing file size without sacrificing quality. Use the right image format (JPEG for photos, PNG for graphics, and WebP for smaller sizes and better quality). Add descriptive, keyword-rich alt text and ensure images are responsive for mobile devices.

What image formats are best for SEO?

For SEO, JPEG is ideal for photos, while PNG is better for images with transparency and graphics. WebP is a newer format that offers high-quality images with smaller file sizes, making it excellent for SEO. Choosing the right format based on the image type can help optimise performance.

Should I include images on every page?

Including images on your website is generally a good idea for SEO, as they can increase engagement and help break up text. However, ensure that each image is relevant to the content of the page and optimised for fast loading times. Avoid overloading pages with too many images, as it may slow down performance.

Can image sitemaps help with SEO?

Yes, image sitemaps can help search engines discover and index your images more efficiently. If you’re using a plugin like Yoast SEO, you can generate an image sitemap, which ensures that your images are properly crawled and indexed by search engines.

How do I know if my images are optimised for SEO?

You can check your images' performance by testing page load speeds using tools like Google PageSpeed Insights or GTmetrix. Also, ensure that your images are properly sized, have descriptive alt text, and are in the right format for SEO.

Does image optimisation affect mobile SEO?

Yes, image optimisation directly impacts mobile SEO. Since mobile users are more sensitive to page loading times, optimising images for faster load speeds on mobile devices is crucial. Make sure images are responsive and adjust automatically based on screen size.

How often should I optimise images?

You should optimise images whenever you upload new content or update existing pages. Additionally, it’s good practice to regularly review and optimise old images, especially if the page’s load speed or SEO performance is impacted.

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