PageSpeed Insights (https://pagespeed.web.dev/) evaluates a webpage’s performance on both mobile and desktop, assigning a score from 0 to 100 based on various core metrics. These metrics are grouped within four areas:
- Performance
- Accessibility
- Best Practice
- SEO
Google officially considers page experience signals, including Core Web Vitals (more about that later), as part of its ranking algorithm. However, you should remember that this is part of a much wider and complex set of rules that govern ranking position.
In this article, we focus on the Performance section of the PageSpeed Insights (PSI) scoring system.
Performance Score
The ‘Performance’ section of Google’s PageSpeed Insights evaluates how quickly a web page loads and becomes interactive, using a number of key metrics including:
- First Contentful Paint (FCP) measures the time until the first text or image appears, indicating how quickly the page begins rendering.
- Speed Index assesses how fast visible parts of the page are populated.
- Largest Contentful Paint (LCP) focuses on the time it takes for the largest visible content element to load, often a hero image or headline.
- Interaction to Next Paint (INP) measures responsiveness to user interactions.
- Time to Interactive (TTI) gauges when the page becomes reliably responsive to user input.
- Total Blocking Time (TBT) quantifies delays caused by scripts blocking the main thread between FCP and TTI.
- Cumulative Layout Shift (CLS) measures visual stability, identifying how much content shifts unexpectedly during load.
These and other factors are combined into an overall Performance Score, giving developers a snapshot of how their site performs on both mobile and desktop, and highlighting specific areas for improvement. The term ‘Core Web Vitals’ refers to LCP, INP and CLS and is the ‘backbone’ of the Performance section.
To improve PSI Performance scores without compromising functionality, Realnet targets a number of best practice considerations for our websites:
- Compress and serve next-gen images (e.g. WebP)
- Minimise unused CSS/JS and enable code splitting
- Implement server-side caching and CDN delivery
- Prioritise content loading with proper resource hints (using specific HTML tags or HTTP headers to instruct the browser ahead of time about which resources are most important, so it can optimise loading order and improve page speed).
The Challenges of Scoring High in Performance
Despite its clear importance, achieving a high Performance score can be deceptively difficult. Here are some of the top issues faced by web developers:
1. Third-Party Scripts
Many websites rely on external services such as ads, analytics tools, chat widgets, or social media embeds that introduce latency. These use scripts (typically JavaScript) that often load asynchronously or block critical rendering paths (steps taken by your browser to convert HTML, CSS, JavaScript etc. into visuals on your screen). This can hurt performance scores despite being essential for functionality.
2. Rich Media Content
High-quality images, videos, and animations are great for engagement but heavy on load times. While compression and lazy loading help, balancing visual appeal with performance remains a technical juggling act.
3. Mobile Constraints
Mobile PSI scores are often lower due to slower network conditions, smaller processors, and more variability in device capabilities. What works smoothly on a desktop may crawl on a mid-range smartphone.
4. Framework & Platform Overhead
Modern web platforms like WordPress, Shopify, or React-based frameworks come with baked-in features and code bundles. While these improve developer productivity, they often introduce render-blocking resources and unused CSS and JavaScript.
5. Server and Hosting Limitations
Even with frontend optimisation, backend factors such as server response time, time to first byte (TTFB), or lack of caching can bottleneck performance. Shared hosting or legacy infrastructure can significantly drag down scores.
Balancing Real-World UX with Scores
It’s important to remember that PSI is a tool and not the end goal. While striving for an excellent score, developers and marketers also need to prioritise real-world user experience. A site with a lower Performance score but fast perceived speed and intuitive design may outperform a high-rated site with poor quality content and over-complicated user experience.
PageSpeed Insights provides a powerful lens into how well your site performs. However, it’s just one piece of the puzzle. Instead of chasing perfection, aim for consistent, measurable improvements that enhance both your user’s experience and your site’s visibility. This may require compromise in terms of functionality and content quality (in terms of, say, image resolutions) but your website provider should be able to help you understand and balance this.
With our website hosting and support services, Realnet can help you make sense of PageSpeed Insights and Core Web Vitals so that you feel confident in your website performance. Get in touch with our online experts today to see how we can help you!