What is PageSpeed and why it should be 100/100

When you show your website to a potential customer, the first thing they see is the design. When Google analyses it, the first thing it measures is the speed. And the score it gives has a specific name: PageSpeed.

PageSpeed is Google’s official scoring system for web performance. It runs from 0 to 100, measures mobile and desktop separately, and is free: you can test your website right now at pagespeed.web.dev. If your score is below 90, you have a problem. If it is below 50, you are losing customers every single day without realising it.

1. What PageSpeed actually measures

PageSpeed is not a single metric. It is the result of analysing your website against dozens of technical parameters and summarising them into a global score. The three most important are the Core Web Vitals, which Google turned into an official SEO factor in June 2021.

LCP (Largest Contentful Paint): how long it takes for the largest element on the page to appear, usually the main image or the title. The target is below 2.5 seconds. If it takes more than 4 seconds, the website is considered slow.

INP (Interaction to Next Paint): how long the page takes to respond when a user interacts with it (clicking, typing, scrolling). The target is below 200 milliseconds. If it takes more than 500 ms, the experience feels “sluggish and unstable”.

CLS (Cumulative Layout Shift): how much the elements on the page shift while loading. When you are about to click a button and it suddenly jumps because an image appeared late, that is CLS. The target is below 0.1.

Beyond Core Web Vitals, PageSpeed measures other factors: time to first byte, total page size, number of requests, JavaScript usage, image optimisation, custom fonts and caching.

2. Why Google penalises slow websites

Google has a very simple goal: serve results that users want to click and that load quickly. If it sends people to a website that takes 8 seconds to load, the user hits back and tries another result. That makes the search engine lose trust. To avoid it, Google ranks fast websites higher.

The data backs it up: according to a Google study, websites with a 1-second load time have a 9% bounce rate. With a 5-second load time, the bounce rate jumps to 38%. 53% of mobile users abandon a page if it takes more than 3 seconds to appear.

And it is not just about traffic. Speed has a direct impact on sales. Walmart calculated that every 100 milliseconds of improvement in load time increased sales by 1%. Amazon reached the same conclusion: 100 ms = 1% more sales.

At an SMB scale, the useful way to look at it is to run the calculation with your own numbers: take your monthly visits, your current conversion rate and the average value of a customer. If slowness is costing you a third of your conversions, that figure is what not fixing it costs you every month. In most businesses it works out more expensive than the work of fixing it.

3. Why most websites do not reach 90

If you measure your business website right now at pagespeed.web.dev, it is likely that the mobile score is below 50. It is not your fault, it is a predictable consequence of how most websites have been built over the past 10 years.

Cause #1: WordPress with too many plugins. Each plugin adds JavaScript and CSS code to your site. 30 plugins can easily add 2 MB of code that loads every time someone opens a page. Heavy plugins like Elementor or WPBakery can add 5 MB on their own.

Cause #2: Unoptimised images. A photo taken with a phone weighs between 3 and 8 MB. If you upload it directly without optimising, every visitor has to download those megabytes. Multiply that by 10 images per page and you have a website that is practically unusable on mobile.

Cause #3: Third-party scripts. Google Analytics, Facebook Pixel, live chat, Google Maps embeds, embedded videos. Every third-party script adds delay. A website with 8 external scripts can take 2 seconds just to load them.

Cause #4: Cheap shared hosting. If you pay 5 EUR a month for hosting, you share the server with 200 other websites. When one of them gets a traffic spike, yours slows down. The server never responds quickly.

Cause #5: No caching, no CDN. Without caching, every visit forces the server to generate the page from scratch. Without a CDN, every user downloads your files from a single server, adding milliseconds to every element depending on the distance.

4. What it takes to reach 100/100

Reaching 100/100 is not impossible: it is a matter of architecture. These are the 6 technical decisions that make it possible:

1. Pre-generated static pages. Instead of generating each page on the server every time someone requests it, you generate every page once when you publish. The server only sends pure HTML, with nothing to execute. Astro, the framework we build websites with, works exactly that way.

2. Images in WebP or AVIF format. WebP reduces image file size by 25% to 35% compared to JPG, with no visible quality loss. AVIF reduces it even more (up to 50%). Each image should have a mobile and a desktop version, with exact sizes.

3. Minimal JavaScript, only where needed. A homepage does not need JavaScript to load. The menu, the buttons, the forms: everything can work with pure HTML and CSS. JavaScript only needs to be added where there is real interactivity (a map, a chat).

4. Custom fonts with font-display: swap. If you use Google Fonts or custom typefaces, they should load in a non-blocking way. That means the text first renders with a system font and then swaps to your custom one once it has been downloaded, without blocking the load.

5. Global CDN. Vercel, Cloudflare and Netlify distribute your files across hundreds of servers around the world. When someone visits your site from Berlin, they download the files from the nearest server, not from the other side of the continent.

6. Total removal of unnecessary third-party plugins. Every live chat, every testimonials widget, every heavy cookie banner drags the score down. There are lightweight alternatives for everything.

5. How to measure PageSpeed correctly

There are three places where you can measure your website’s performance. They are all free, but they will give you slightly different results.

pagespeed.web.dev is Google’s official tool. It measures mobile and desktop separately, shows the Core Web Vitals and gives you a list of issues with concrete suggestions. It is the most reliable option for an initial diagnosis.

Lighthouse is a tool built into the Chrome browser (right click > Inspect > Lighthouse). It lets you run audits from your own computer. Useful when you want to test changes locally before publishing.

GTmetrix is an alternative with more visual reports and historical tracking. Useful for monitoring how the website evolves over time.

Important: the mobile score is what matters. Google indexes the mobile version of your website first (mobile-first indexing) and there are more users browsing from mobile than from desktop. If your mobile score is 40 and your desktop score is 95, you have a serious problem.

6. What happens if you have a low score

Not everyone needs to score 100. But there are thresholds that signal risk:

If your score is below 70, this is not a cosmetic issue: it is a business issue. Every month that passes, you lose traffic, you lose conversions and you lose rankings.

How we approach it

At serpixel we build websites with Astro, a framework designed from day one for speed. We generate static pages, optimise images to WebP, keep JavaScript to the bare minimum and serve everything from a global CDN.

This is not a scoring trick: it is what makes a high score the website’s normal state rather than a one-off milestone that deflates within three months. No architecture guarantees a number, because the score also depends on what you add afterwards (a marketing script, an embedded video, an image uploaded without optimisation). What you can do is measure it regularly and correct it when it drops, on an agreed cadence.

If you want to know your website’s current PageSpeed, start with yourself: run it through pagespeed.web.dev, look at the mobile score and note the top three problems it lists.

If you do not like the number and want to understand what fixing it properly would take, let’s talk it through in 30 minutes. We go over the report together and tell you whether it is a matter of tweaks or whether the architecture is the problem.