How to optimise images for SEO

When it comes to SEO, it pays to be thorough, and that includes optimising your images.

After working hard on optimising your written content and choosing the best photos or illustrations for your web pages, make sure your website’s performance isn’t held back by your use of imagery.

Users typically have a low tolerance for slow-loading web pages and many people expect a page to load in under a couple of seconds. Google has found that 53% of visits are abandoned if a mobile site takes over 3 seconds. Any longer, and visitors are likely to go elsewhere – probably to a competitor site.

What is image SEO?

Image SEO refers to the practice of optimising images to improve visibility and ranking in search engine results. It’s essential to include this in your SEO strategy to help drive traffic via Google Images, as well-optimised images can significantly enhance your website’s reach.

Your goal should be to ensure that any images you feature on your website are accessible and load quickly so that they can contribute positively to your SEO and provide a great user experience (UX).

To optimise an image effectively, you need to consider file format, image size, file name and alt text. Also, make sure that your images are responsive for all devices and that they contribute to an easy, smooth experience to improve page performance.

By optimising your images, you could boost both image performance and search visibility – it’s a win/win situation.

Read about why SEO fails in 2024 and what you can do about it.

Why should you optimise images for SEO?

Optimising images for SEO is an important aspect of improving a website’s overall search engine performance and user experience.

Here’s why it’s worthwhile optimising your images:

Better page load speed – Optimised images are typically smaller in file size, which helps web pages load faster. Faster loading times enhance user experience and can positively impact search engine rankings, as page speed is a known ranking factor.

Better user experience – When optimised, images load quickly and display correctly, providing a seamless user experience. A positive user experience can lead to longer site visits and lower bounce rates, both of which are favourable for SEO.

Enhanced accessibility – By adding descriptive alt text to images, you improve accessibility for users with visual impairments who rely on screen readers. Alt text also provides search engines with context about the image content, improving indexation.

Increased visibility in image search – Optimised images with relevant alt text and file names can appear in image search results, driving additional traffic to your site. With an estimated 20-30% of all searches on Google related to images, that could be a lot of traffic.

Reduced bandwidth usage – Smaller image files require less bandwidth, which can reduce hosting costs and improve site performance, especially for mobile users.

Improved mobile experience – Optimising images is crucial for mobile users, who may experience slower load times due to network limitations. Mobile-friendly sites are also favoured in mobile search rankings.

SEO ranking signals – Properly labelled and optimised images can contribute to SEO ranking signals, as search engines can better understand your page’s content and relevance.

Keyword optimisation – Using relevant keywords in image file names and alt text can help search engines understand the context of your content, aligning with targeted search queries.

Read the ultimate guide to SEO web design.

How can I optimise my images?

Follow our step-by-step guide to image SEO optimisation

Step 1. Choose the right format

JPEGs are best for photographs and images with complex colours and gradients. It provides good compression, which reduces file size while maintaining image quality. PNG files are ideal for simpler images such as graphics or logos (where maintaining sharp edges and high resolution is important) or pictures that need transparency.

Step 2. Resize large images

Adjust images to the exact dimensions your site needs to avoid large files that slow down loading times. By resizing images to fit specific display areas, you ensure that they load quickly and efficiently. You can use image editors for resizing. They typically have user-friendly interfaces and features that allow you to tailor your images to the ideal dimensions for your web pages.

Step 3. Compress your images for speed

Reducing the file size of images without compromising quality helps improve page load speed, which is a ranking factor for SEO. Tools and plugins can be used to compress images efficiently.

Step 4. Optimise your image file names

Using descriptive, keyword-rich file names for images helps search engines understand what the image is about. For example, instead of a generic name like ‘IMG006.jpg’, go for something specific such as ‘glass-of-iced-coffee.jpg.’ This improves SEO by making your images more discoverable and helps to keep your website’s media library organised.

Step 5. Write descriptive alt text

Alt text (alternative text) is a short description of an image that helps search engines and screen readers understand the content of the image. It should be concise, relevant, and include keywords where appropriate. For example, if you have an image of a glass of iced coffee, your alt text could be ‘chilled glass of iced coffee with a straw on a wooden table’, which describes the image accurately and includes keywords like ‘iced coffee’.

Step 6. Ensure responsiveness

Make sure your images look their best on all devices. By using HTML code, you can deliver various image sizes depending on the screen size and resolution, which helps optimise loading times and display quality across different devices. CMS platforms have built-in features or themes that automatically adapt images for different screen sizes – otherwise, you can use online tools to help.

Step 7. Implement lazy loading

Delay the loading of images until they are needed by using ‘lazy loading’ techniques, which means images are loaded only when they are about to enter the visitor’s view as they scroll down the page. This improves page load times and performance by reducing the initial load time and allows the main content to appear more quickly.

Step 8. Remove any unnecessary metadata

Strip out extra data – like camera settings – to reduce image file size. This metadata isn’t necessary for web display and only adds to the file’s size, slowing down load times.