Image optimisation - how to reduce size without losing quality?

Did you know that images account for, on average, over 50% total website weight? In a world where every millisecond of delay can mean losing a customer, optimising images on a website for SEO is becoming a key element of a performance strategy. It is not just a question of graphics looking good – above all, they must be „lightweight” and fully understandable to search engine algorithms.

High visual quality doesn’t have to come at the expense of speed. Thanks to modern compression technologies and smart file formats, we can serve users beautiful images that load in the blink of an eye. Below is a comprehensive guide to help you slim down your website without compromising its professional appearance, which will directly improve your Google rankings and enhance the experience of users browsing your site on mobile devices.

File formats: WebP and AVIF as the new standard in 2026

Choosing the right format is the first and most important step in the optimisation process. Traditional formats, although still common, are increasingly giving way to more modern solutions that offer a much better balance between quality and file size. The choice of file format should depend on what the image depicts.

• JPEG (Joint Photographic Experts Group): It is a classic of its kind and remains a good choice for highly complex images with a vast amount of detail, where lossy compression is acceptable. However, in most cases, it should be replaced by the WebP format by 2026.
• PNG (Portable Network Graphics): It is essential whenever you need lossless quality or transparency (e.g. logos, icons with an alpha channel). Unfortunately, these files are usually very large, so it is best to use them sparingly.
• WebP: A modern format developed by Google. It offers file sizes that are approximately 25–35% smaller than JPEGs whilst maintaining the same visual quality. It is currently the „gold standard” on the internet and is supported by all modern browsers.
• AVIF: An even more efficient successor to WebP. It offers incredible compression, although it is worth checking support on older systems before implementing it via Can I Use – WebP/AVIF format support.

Using next-generation formats is the simplest way to improve your performance test results. If your website still relies solely on heavy .jpg or .png files, you’re missing out on the chance to rank higher and putting off users with slower internet connections.

Compression tools and techniques – how to lose weight sensibly?

Reducing the file size does not necessarily mean a visible deterioration in image quality, i.e. so-called pixelation. Thanks to intelligent compression, you can reduce the file size by as much as 70–80%, whilst retaining the sharpness of detail that is important to the user. This process involves removing unnecessary metadata and optimising the way colours are stored.

Recommended optimisation tools:

1. Squoosh: A free tool from Google that allows you to compare the quality before and after compression in real time and experiment with different codecs directly in your browser.
2. TinyPNG / TinyJPG: The most popular choice for fast, bulk optimisation of PNG and JPEG files. It uses intelligent lossy compression, which is virtually imperceptible to the human eye.
3. ImageOptim: An excellent, free tool for macOS users that removes unnecessary data from image files without any loss of visual quality.

In professional projects, optimisation should be part of the automation process (e.g. using scripts in Node.js or plugins in CMS systems). This ensures that every image uploaded by an editor is automatically converted and compressed into the lightest possible format. You can read more about how overall performance affects SEO in our article Website speed and Core Web Vitals.

SEO aspects of graphics: It’s not just about bytes, but also about content

Google Search does not „see” images in the same way as humans do. Its algorithms need additional textual clues to understand what an image depicts and whether it is relevant to the user’s query. Optimising images on a website for SEO It therefore includes several key metadata elements that contribute to a website’s authority:

• The ALT attribute (alternative text): This is by far the most important element. This text is read by screen readers for visually impaired people and indexed by Google’s web crawlers. It should describe the image’s content in a natural way, whilst including relevant keywords, but without overloading it with them.
• File naming conventions: Avoid generic filenames such as „IMG_1234.jpg”. Instead, use descriptive phrases separated by hyphens, for example „effective-image-optimisation-for-SEO.webp”. This provides an additional signal to search engines about the page’s subject matter.
• Graphics sitemap: If your website relies heavily on visuals (e.g. an e-commerce site or a portfolio), add images to your sitemap. This will help Google’s crawlers find and index your media more quickly in the image search.
• Google Image Search: Remember that image search is a powerful source of additional organic traffic, particularly in the fashion, food and travel sectors, where users often start their research by browsing photos.

If you’re just starting out with professional SEO and want to assess your website’s current status, it’s worth taking a look at our guide SEO audit – where to start?.

Responsive Images and Lazy Loading – technology in the service of UX

There’s no point in sending a huge 2500-pixel-wide image to a small smartphone screen. The solution is responsive images, implemented using appropriate attributes in the page code. This allows the browser to select the version of the file best suited to the screen width of the device on which the page is being displayed, which drastically reduces data usage and loading time.

Technology provides additional support Lazy Loading. This ensures that images located below the fold are only loaded when the user scrolls down to them. This allows the browser to focus on instantly displaying what the user sees right at the start. This is a key element of mobile optimisation, where connection stability can vary.

Advanced structural data for multimedia

To ensure your images stand out in search results and catch the eye, it’s worth implementing structured data (Schema.org). This is particularly important for recipes, where a photo of the finished dish appears alongside the search result, and for products in online shops, where a thumbnail may include information about price or availability.

Properly marking up images allows Google to display so-called „Rich Results”, which have a significantly higher click-through rate (CTR) than standard text links. As a result, your website not only loads faster but also becomes more visually appealing even at the stage of browsing the search results list, which directly translates into increased traffic.

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Summary: Every kilobyte matters to your business

Optimising images is one of the simplest and most effective ways to significantly speed up a website. By using modern WebP and AVIF formats, ensuring correct ALT attributes, and implementing responsive techniques, you build a website that is user-friendly and Google-friendly. In an era where Core Web Vitals are playing an increasingly important role, neglecting this area could cost you a drop in rankings that could easily be avoided.

At 4ADStudio, we know exactly how to combine aesthetics with uncompromising performance. Our projects prove that a website can be full of beautiful visuals and high-quality photography without compromising on loading times or performance.

Is your website taking too long to load because of heavy images? Do you want your photos to generate real traffic from Google Images and attract new customers? Get in touch with us – we’ll carry out a professional optimisation of your website and make it lighter, faster and more visible online than ever before!