Website performance 101: what it is, why it’s important, and how to measure it

Today’s internet users expect nothing less than a seamless experience. Visitors will get frustrated and go elsewhere if your website takes too long to load, features an unstable page layout, or proves difficult to navigate. 

And it’s not just your website visitors who demand (near) perfection. Google will penalize you in search results if your website performance isn’t up to par. 

So, it pays off to spend a little time getting this right. But—what exactly do we mean by ‘website performance’, and why is it so important? Moreover, how do you measure your own website performance, so you can learn to improve it? Read on for the answers to all these questions. 

What is website performance? 

Website performance is a measurement of how responsive your website is across different devices and how quickly it loads, providing insights to help you optimize your site for speed and ensure it’s as user-friendly as possible.

Definitions of website performance also increasingly take into account user experience (UX)—quantitative data and qualitative observations on how intuitive your site is to use. 

Web performance optimization (WPO) is the practice of improving the performance of your website through different techniques, such as image optimization, avoiding 301 redirects, implementing a CDN, and browser and server caching.

Why is website performance important?

Web performance has a massive impact on your customer experience, and affects everything from your search engine rankings to overall revenue. 

A high-performing website—that is to say, a fast, stable, responsive website with smooth UX— helps you

• Reduce your bounce rate: studies show that even a 1-second delay in load time can lead users to leave your site prematurely. Conversely, a well-optimized site will keep visitors coming back for more. 

• Improve your brand reputation: nothing makes your business appear unprofessional or unreliable like a poorly functioning website. Conversely, a smooth, reliable experience fosters trust and encourages users to engage with your offer. 

• Boost your conversions: website performance directly affects revenue. Faster ecommerce sites, for example, typically see improved sales figures, with a 1-second reduction in load time corresponding to a conversion rate increase of 5.6%.

• Strengthen your SEO: search engines like Google prioritize website performance. Speed, stability, and mobile-friendliness play a key role in search rankings, so a slow or clunky website is less likely to appear on the first page of search results. Since most users rarely go beyond the first page, poor performance can significantly reduce organic traffic and visibility.

Key metrics to track to measure web performance

Measuring your website performance means tracking key metrics that speak to your site’s speed, responsiveness, and user experience. Here are the most important ones to keep an eye on:

Google’s Core Web Vitals

We can’t talk about website performance without mentioning Core Web Vitals: 3 evaluation criteria which, since 2021, Google’s algorithm has been taking into account when deciding the order of search results. These criteria are: 

• Largest contentful paint (LCP), or simply your website load speed. It’s the time it takes for a page’s primary piece of content to load. It marks the exact moment when the largest piece of content such as an image, video, or text block on the first section of each page is fully loaded. According to Google, the average rate of a correct LCP is about 2.5 seconds.

• First input delay (FID) is the delay users experience when interacting with the page for the first time. It measures the responsiveness of the web page. The rate recommended by Google is 100 ms or less.

• Cumulative layout shift (CLS) measures page stability by monitoring significant movements of the elements on the page that may frustrate or mislead the user. If you’ve ever experienced a sudden shift while on a page, like an image or text changing its place, it’s due to CLS. Google recommends that you keep your CLS score under 0.1.

Page load speed metrics 

Another ranking factor for Google search results is page speed. Faster-loading sites generally appear higher in search engine results pages (SERPs) than slower-loading ones. Here are some related metrics to look out for: 

• Time to first byte (TTFB) measures the time between the browser requesting a page and the moment the user receives the first piece of data. Faster response times improve overall page speed. 

• Fully loaded time is the total time it takes for all page elements to load completely.

• Speed index measures the display speed of the pixels included in the visible part of the tested web page—above the fold. Google recommends a speed index of 0–1.3s on desktop or 0-3.4s on mobile. 

• Visually complete measures how long it takes for all content above the fold to be visible, in its final form 

• Time to consistently interactive, also known as time to interactive, measures the time it takes for a page to be durably interactive—when all conditions are met for at least 5 seconds for an interaction to happen in a satisfactory way 

UX-related metrics 

• Bounce rate: the percentage of visitors who leave your site after viewing only one page. High bounce rates may indicate slow load times or poor content relevance.

• Session duration: how long users stay on your site. Longer sessions are generally preferable, since they indicate engaging content—but they could also mean your users are not finding what they’re looking for. 

• Pages per session: measures how many pages a user visits per session. A higher number suggests good navigation and compelling content.

• Conversion rate: tracks the percentage of users who complete a desired action (like making a purchase or signing up for a newsletter). A low conversion rate could indicate performance or usability issues.

• Rage clicks: identify when users repeatedly click on an unresponsive or broken element, signaling frustration and potential technical issues

💡 Pro tip: use Contentsquare Dashboards to measure quantitative UX metrics, such as bounce rate, conversion rate, session duration, and rage clicks. The platform allows you to create an unlimited amount of custom dashboards featuring whichever mix of metrics is the most relevant to your project. You can also sign up to receive automated Alerts when there’s a significant change to any of these numbers.

4 tools to measure web performance

The first step to improving your web performance is measuring your site’s current performance. This gives you a benchmark to track progress as you make improvements. Here are some key tools for collecting data for a web performance report. 

1. Google’s PageSpeed Insights 

Google’s Page Speed Insights is arguably the most used website speed analysis tool. It gives a good snapshot of your Web Core Vitals and the performance of your site through one single test. It provides results for both mobile and desktop sites, as well as helpful tips on how to make improvements.

The tool shows an overall score that summarizes the page’s simulated performance. A score of 90 or above is considered good, any score between 50 to 90 needs improvement, and below 50 is considered poor.

2. Contentsquare’s Speed Analysis  

Contentsquare’s Speed Analysis allows you to continuously monitor and optimize your web pages. Use it to easily keep tabs on your Core Web Vitals and site speed metrics. 

Speed Analysis offers synthetic monitoring, so you can test your pages’ performance on different devices and from different locations—before users even interact with them. So if your site loads slowly in Japan, you’ll be notified before your first Japan-based user even enters your site. 

Unlike many website performance tools, Contentsquare’s Speed Analysis contextualizes your data with further insights. Your analysis data comes with personalized recommendations for improvements, so you can move more easily from “This is where our web performance is at right now” to “This is how we’re going to improve it in the future.”

Contentsquare’s Speed Analysis offers personalized recommendations to help you improve your site’s speed

3. WebPageTest  

WebPageTest is a tool available via the Catchpoint platform. It allows you to test your website’s performance—site speed metrics, Core Web Vitals, and even search page rankings—using real browsers, devices, and locations worldwide.

Use WebPageTest to diagnose slow-loading elements, detect render-blocking resources, and get optimization suggestions. There’s a free trial to get you started. 

4. Pingdom 

Pingdom keeps tabs on your key performance metrics—including Core Web Vitals. Like Contentsquare’s Speed Analysis tool, it uses synthetic monitoring (tests that simulate user visits) and real user monitoring (which entails tracking actual visitor behavior).  


Use Pingdom to understand your site’s site availability, response times, and performance trends over time. You can even set up alerts to be notified when your site experiences slowdowns.

💡 Pro tip: once you’ve used one of the above tools to keep track of your Core Web Vitals and page load speed metrics, it’s time to show your UX-related web performance metrics some love. That’s where a multi-tool experience intelligence platform like Contentsquare comes in handy. 

if you spot any unexpected results, dig into qualitative UX data using tools like Heatmaps and Session Replay. Heatmaps are color-coded data visualizations that show user behavior like clicks, taps, and scrolls in aggregate. Session replays are recordings of user sessions, which reveal exactly what your users did and saw. So, for example, if a page’s bounce rate increases, you could open a heatmap to see where customers are clicking on that page, and watch some session replays to understand where they might be getting lost. 

Taken together, these quantitative and qualitative data points allow you to comprehensively ‘measure’ your UX—a vital part of your website’s performance.

Cross-reference your quantitative UX data with qualitative tools like heatmaps

Prioritize your website performance for better business outcomes  

If you’ve gone through the trouble of launching and maintaining a website, ensuring its performance is up to scratch should be high on your list of priorities. Unless your site is sufficiently fast, responsive, and reliable, Google won’t serve it to users in search results on a silver platter—and the users who do find it will be in for a bumpy ride.

To deliver the smooth experience your users expect, monitor your website’s performance regularly with the tools above and be prepared to make any necessary adjustments. You’ll quickly feel the benefit to your customer retention, search engine rankings, and bottom line. 

FAQs about website performance