Sam Champion Sam Champion

According to Forbes, 76% of consumers have abandoned carts due to slow websites, with 39% walking away from purchases of £100 or more.

Today, speed is everything; visitors expect instant access to information, and anything less can lead to lost traffic and missed opportunities. One of the leading causes of slow websites is the use of large, unoptimised images. Image optimisation involves preparing your images to have the smallest possible file size while maintaining a professional and sharp appearance. This process typically includes resizing, compressing, and selecting the best file format for each image. When done correctly, image optimisation helps your site load faster, improves the user experience, and can even boost your visibility in search engine results pages (SERPS).

Read on to understand why image optimisation is vital for modern websites, the potential risks of ignoring it, the effect on your SERP rankings and the top tools that can help increase your site’s speed and effectiveness.

Why optimising images is important

Images often make up the largest share of a page’s total bytes, so how you prepare them directly affects performance and user experience (UX). Optimising means resizing, compressing and using the right format to keep file sizes small while maintaining visual quality. When done well, this makes your site look professional, load quickly and keeps visitors engaged.

  • Faster loading and happier users – Large image files can delay the main content from appearing, which negatively impacts Largest Contentful Paint (LCP). This Core Web Vitals metric measures how long the biggest visible element (for example, a hero image or headline) takes to render fully. As part of Google’s Core Web Vitals, it’s recommended to keep LCP under 2.5 seconds. Heavy images also strain the device during decoding, which can negatively impact Interaction to Next Paint (INP), a metric that reflects responsiveness.
  • Stronger search engine optimisation (SEO) – Search engines use crawlers, such as Googlebot, to fetch pages and follow links. Your crawl budget controls how many URLs are requested over time, influenced by server health and site importance. Large, slow pages, often caused by oversized images, increase latency and timeouts, causing bots to back off, which results in fewer pages being discovered or refreshed. This delays indexing and may limit rankings and organic traffic.
  • Better performance on mobile – Mobile networks fluctuate, and many devices have less CPU and memory capacity than desktops, so oversized images have the most significant impact on mobile users. Smaller, efficiently compressed assets load more reliably, use less data, and even reduce battery drain, thereby enhancing accessibility and overall user experience across various devices and conditions.
  • Lower costs and greater scalability – Heavy images consume more bandwidth, storage, and content delivery network (CDN) egress fees, and they also increase server load during peak traffic. Well-compressed assets reduce infrastructure strain, improve cache efficiency and keep costs predictable as traffic grows. By providing appropriately sized images for different devices, utilising long-lived caching, and adopting modern image formats, you can ensure that each device receives only the content it needs.
  • More consistent brand presentation – Crisp, correctly sized images prevent pixelation and compression, which can make brands look unpolished. Serving dimensions tailored to each viewport and device pixel ratio keeps visuals sharp and consistent across screens. Standardising formats, colour profiles, and aspect ratios ensures a cohesive, professional look in every context.

In short, optimised images bring meaningful content to the screen faster, which strengthens Core Web Vitals and makes it easier for search engines to crawl and rank your pages.

How image optimisation impacts SEO

Optimised images make pages faster, clearer, and easier for search engines to understand – improving both rankings and visibility in standard and image search.

Page speed as a ranking factor

Faster pages tend to rank better because speed is part of Google’s Core Web Vitals (CWV), a set of user‑centric performance metrics. Trimming image bytes helps meet targets such as Largest Contentful Paint (LCP) under 2.5 seconds, Interaction to Next Paint (INP) under 200 milliseconds, and Cumulative Layout Shift (CLS) under 0.1. Lean images also reduce server latency, which improves crawl efficiency and helps more pages get indexed.

Improved user experience and engagement

Smaller, well-compressed images reduce waiting time, increase perceived responsiveness, and lower bounce rates – signals that support better search performance. Research cited by Google reports that 53% of mobile visits are abandoned if a page takes more than 3 seconds to load, highlighting how image bloat directly harms engagement.

Image search visibility

Clear, descriptive alt text, easy-to-understand file names, and structured data (for example, ImageObject) help images appear in Google Images and rich results. Ensure images are discoverable (not blocked by robots.txt), provide width/height for a stable layout, and serve high‑quality assets (at least 1200 px wide) for eligibility in rich surfaces like Discover.

Top tools for image optimisation

Tool What is it? Key features
Cloudinary A service that stores your images and automatically delivers the right size and format to each visitor. Resizes and compresses images on the fly, converts to modern formats (like WebP/AVIF), and uses a global network to load images fast.
Imgix A fast image service that lets you change image size and quality by adding simple options to the image URL. Quick resizing and compression, smart cropping (which keeps faces in frame), and support for modern formats.
ImageKit An easy-to-use image service with a built-in library and fast delivery. Automatically picks the best format and quality, shows quick-loading placeholders, and pulls images from your existing site.
Squoosh A free website from Google to manually compress images and see quality changes in real time. Side-by-side comparison, multiple formats (like AVIF and WebP), and runs in your browser.
ShortPixel A WordPress-focused tool that compresses your media library and can convert images to modern formats. Bulk optimisation, WebP/AVIF conversion, backups, and an optional CDN.
Kraken.io An online and API-based image compressor for everyday use. Lossy and lossless compression, URL import, and plugins for popular systems.
Imagify A beginner-friendly WordPress plugin to compress images in bulk. One-click optimisation, WebP support, and easy settings for adjusting the compression level.

10 quick tips for image optimisation

Here are straightforward, high-impact steps you can apply today to make images lighter, faster, and cleaner – without sacrificing visual quality. Use them as a quick checklist during export and when adding media to your site:

  • Resize images to the size they’ll actually appear on the page. Do not upload 4000px images for a 1200px slot.
  • Use modern formats first (AVIF or WebP) and fall back to JPEG/PNG for older browsers.
  • Compress at a medium setting and check by eye; don’t aim for 100% quality as file size increases with little benefit.
  • Add width and height (or a fixed aspect ratio) so the layout doesn’t jump around while images load.
  • Serve different sizes for different screens with responsive images (srcset and sizes) so mobile devices don’t download desktop-sized files.
  • Cache images for a long time and utilise a CDN to ensure they load quickly from a location near your users.
  • Export to sRGB and strip unnecessary metadata (such as EXIF) to keep files smaller and prevent leaking device/location information.
  • Write clear, descriptive alt text for meaningful images; leave decorative images without alt text.
  • Set upload rules in your CMS (max width/height and file size) to prevent oversized images from slipping through.

Image optimisation is one of the most effective, low-risk ways to boost speed, improve Core Web Vitals and strengthen SEO – without sacrificing visual quality. By pairing the right formats and sizes with smart delivery (responsive markup, lazy loading, caching, and a CDN), you deliver a faster, cleaner experience that keeps users engaged and helps your business grow.

Book a free consultation with us today, and we’ll translate your business objectives into a focused optimisation strategy.