A fast website is crucial for both your visitors and your position in Google. But how do you measure exactly how fast your website loads? And more importantly: what do all those scores and graphs actually mean? In this article, you will learn how to use and understand the most important speed test tools.

The three most important speed test tools

There are dozens of tools available to measure your website speed, but these three are the most reliable and informative:

Google PageSpeed Insights

This is Google's own tool and therefore extra relevant for SEO. PageSpeed Insights measures both the mobile and desktop performance of your website. The tool is based on real user data from Chrome (Core Web Vitals) and simulated tests.

Important metrics you see here:

  • Performance score (0-100): A general assessment of your page. Aim for at least 90 for good results.
  • First Contentful Paint (FCP): How quickly the first content becomes visible. Ideal under 1.8 seconds.
  • Largest Contentful Paint (LCP): When the largest element is loaded. Keep this under 2.5 seconds.
  • Cumulative Layout Shift (CLS): Measures how stable your page is during loading. Under 0.1 is good.
  • Time to Interactive (TTI): When the page is fully usable.

GTmetrix

GTmetrix provides a more detailed picture than PageSpeed Insights and is a favorite among developers. The free version tests from Vancouver, but you can also choose a European server for more relevant results.

GTmetrix shows two main scores:

  • Performance: Based on Lighthouse metrics, similar to PageSpeed Insights.
  • Structure: How well your website is technically built (caching, compression, etc.).

Pingdom Website Speed Test

Pingdom is the easiest to understand and gives a quick impression. You choose a test location and immediately get the load time in seconds. Ideal for a quick check, but less suitable for in-depth analysis.

Understanding the waterfall chart

The most valuable information in any speed test is the waterfall chart. This is a visual timeline that shows the order in which all files load and how long each file takes.

What to look for in the waterfall:

  • Render-blocking resources: CSS and JavaScript files at the top that take long to load block your page from displaying.
  • Large images: Look for files larger than 200KB. These can often be compressed without quality loss.
  • External scripts: Fonts, analytics, and social media widgets often load slowly. Consider if you need all of them.
  • Red or orange bars: These indicate problems. Red often means a file was not found (404 error).

You read the waterfall from top to bottom. The shorter the total timeline, the better. Pay special attention to the first few seconds, as that is where visitors experience the most delay.

What each color means

In GTmetrix and similar tools, you see colored bars for each file:

  • Blue (DNS Lookup): Time to find the server. Usually negligible.
  • Orange (Connecting): Time to establish a connection with the server.
  • Green (Waiting/TTFB): Time To First Byte - how long your server needs to respond. With Theory7 hosting, this is usually very fast thanks to our PHP-FPM configuration.
  • Purple (Receiving): How long it takes to download the file.

Setting priorities for improvements

After analyzing your speed tests, you know where the problems are. But where do you start? Follow this order for the best results:

1. Server response time (TTFB)

If your TTFB is above 600ms, your hosting may be the problem. On Theory7 servers with LiteSpeed web server, you typically achieve under 200ms. Also use caching to reduce server load.

2. Optimize images

This often yields the biggest gains. Compress images with tools like Smush or ShortPixel. Serve modern formats like WebP where possible. Check out our guide about Smush for WordPress.

3. Enable caching

Browser caching ensures returning visitors do not have to reload everything. Server-side caching (like LiteSpeed Cache) speeds up first visits. Read more in our article about LiteSpeed Cache plugin configuration.

4. Optimize CSS and JavaScript

Combine and minify your CSS and JavaScript files. Load non-critical scripts asynchronously or defer them to later. Most caching plugins like WP Rocket and LiteSpeed Cache offer these features.

5. Limit external resources

Every external resource (Google Fonts, social widgets, tracking pixels) adds load time. Consider hosting fonts locally and only load the scripts you actually use.

Practical tips for reliable tests

To get consistent results when testing:

  • Test multiple times and take the average. One-time tests can vary.
  • Choose a test server close to your target audience. For Dutch visitors, a European server is most relevant.
  • Test both your homepage and important landing pages. Not every page loads equally fast.
  • Always compare the same page before and after a change to measure the effect.

Ready to make your website faster? At Theory7, we offer LiteSpeed web servers, PHP-FPM, and SSD storage as standard for optimal performance. Need help optimizing your website? Our support team is happy to help.