Imagine this: you click on a promising website, eager to explore it. Instead of a smooth experience, you get a slow loading screen, and each second feels like an eternity. Few users have that patience: a slow page sends visitors away before they’ve even started.
That’s where website performance optimisation comes in: making sure your website loads quickly and reliably, from the first click. It isn’t only about user experience; it also supports SEO. Page experience, measured by Google’s Core Web Vitals, is one of the signals Google uses, and a slow website, however beautiful or rich in content, makes it harder for visitors to stay and for your pages to compete.
Here’s how to optimise your website for both speed and SEO.
What are Core Web Vitals?
Core Web Vitals are Google’s three metrics for real-world user experience on a page: how fast the main content loads, how quickly the page responds to input and how stable the layout is. Diagnose your bottlenecks with them first:
Largest Contentful Paint (LCP)
How long it takes for the largest element on the page, usually the main image or headline, to appear. Google’s “good” threshold is 2.5 seconds or less.
Interaction to Next Paint (INP)
How quickly the page responds to user interactions such as clicks, taps and key presses, across the whole visit. INP replaced First Input Delay (FID) as a Core Web Vital in March 2024. Google’s “good” threshold is 200 milliseconds or less.
Cumulative Layout Shift (CLS)
How stable the page is while it loads. A low score means content doesn’t jump around under the reader’s finger. Google’s “good” threshold is 0.1 or less.
How do you measure Core Web Vitals?
You measure Core Web Vitals with field data from real visitors and lab data from test runs. Google Search Console’s Core Web Vitals report and PageSpeed Insights show field data from the Chrome UX Report for your pages; Lighthouse and WebPageTest run lab tests that help you find the cause. Google assesses a page on the 75th percentile of real visits, so fix for your slower visitors, not just your own fast laptop.
These metrics are your roadmap. Once you know what’s slowing you down, use these techniques:
Optimising your website for speed
Image optimisation: images are often the heaviest part of a page, but you don’t have to remove them. Reduce file size without losing quality by:
- Compressing images with tools such as TinyPNG or Squoosh.
- Choosing the right format: modern formats such as WebP and AVIF for most images, JPEG for photographs where you need wide support, and PNG or SVG for graphics with transparency.
- Resizing images to the size they’re displayed at, and serving smaller versions to smaller screens.
- Giving every image a width and height, so the layout doesn’t shift as it loads (this helps CLS).
- Loading the main above-the-fold image early, and lazy loading the rest (this helps LCP).
Fewer, lighter requests: every file a page needs, from images to scripts, adds to the load. Reduce the cost by:
- Removing scripts, styles and third-party tags you don’t need.
- Combining small files where it helps; with modern HTTP/2 and HTTP/3 connections, the number of files matters less than their total size and order.
- Lazy loading non-critical content below the fold.
Caching for faster return visits: caching stores frequently used files so later visits are faster. Use both:
- Browser caching: tell browsers to keep static content such as images and scripts for future visits.
- A content delivery network (CDN): serve your content from servers around the world, close to each visitor.
Lighter JavaScript: JavaScript is the most common cause of slow interactions (INP) as well as slow loading. Optimise it by:
Minifying code
Remove unnecessary spaces and characters.
Deferring non-critical scripts
Load them after the main content appears.
Loading scripts asynchronously
Load scripts in parallel without blocking the page from rendering.
Breaking up long tasks
Split heavy work into smaller pieces, so the browser can respond to clicks and taps in between.
Code minification
Minify CSS, HTML and JavaScript to remove whitespace, comments and other non-essentials, which shrinks file sizes and improves loading times.
Hosting matters
Your hosting is the foundation of your website’s speed. Choose a reliable, fast provider with a good track record, and check your server response time (Time to First Byte).
If your site is a web application rather than a marketing site, the back end often matters as much as the page: our guide on how to speed up a slow web app covers server and database fixes.
Optimising for SEO
Speed helps visitors stay, and SEO helps them find you. Optimise your website for search engines with these tactics:
On-page optimisation: keywords help search engines understand what each page is about.
- Use the target keyword naturally in the page title, meta description, headings and content.
- Structure your content logically with headings and subheadings, for readability and crawlability.
- Use internal links to guide users and search engines between related pages.
Mobile-friendliness: Google indexes the mobile version of your pages first, so make sure your site works well on every screen size.
Technical SEO: keep a clean, crawlable site structure, fix broken links, keep your sitemap current and check that robots.txt doesn’t block pages you want found.
Content quality: create high-quality, useful content that matches what people are searching for and keeps them reading.
Backlinks: earn links from relevant, high-quality websites to build your site’s authority.
For the wider strategy, see our guide to SEO strategies for organic traffic.
Tools and resources
- Google PageSpeed Insights: field and lab data for any page, with suggestions.
- Google Search Console: the Core Web Vitals report across your whole site.
- Lighthouse: lab audits for performance, accessibility and SEO, built into Chrome’s developer tools.
- GTmetrix and WebPageTest: detailed loading waterfalls and test settings.
- Moz and other SEO tools: keyword research and site audits.
Conclusion
Website speed and SEO work together. Measure your Core Web Vitals, fix the biggest problems first (usually images, JavaScript and server response time), then keep your content, structure and links strong. A fast, well-structured website keeps visitors engaged and gives your pages their best chance in search.
If you’d like help, see our SEO and AEO services, or, if the fix needs changes to how the site is built, our web development page.