Speed
Running a GTmetrix analysis on WordPress: complete manual
28 February 2025 · 4 min read
GTmetrix is one of the most complete tools for analysing website speed. It combines Google Lighthouse with its own analyses and gives detailed reports on loading times, performance problems and optimisation opportunities.
At WP Maintainer we use GTmetrix daily to monitor the performance of client websites. In this manual we explain how to use GTmetrix optimally.
What does GTmetrix measure?
GTmetrix analyses your website on: - **Performance Score** — combined score based on Lighthouse - **Structure Score** — how good is the technical structure - **Largest Contentful Paint (LCP)** — how fast the largest element loads - **Total Blocking Time (TBT)** — how long the page is not interactive - **Cumulative Layout Shift (CLS)** — how much the layout shifts - **Full loading time** — total time to full rendering
How do you run an analysis?
1. Go to gtmetrix.com 2. Enter your URL 3. Choose a test location (Amsterdam for Dutch sites) 4. Choose a browser (Chrome or Firefox) 5. Choose a connection speed 6. Click "Test your site"
Interpreting the results
Common problems and solutions
**Problem: Slow server response** Solution: Upgrade hosting, implement caching, optimise database.
**Problem: Large images** Solution: Compress images, use WebP, implement lazy loading.
**Problem: Render-blocking resources** Solution: Defer or async JavaScript, inline critical CSS.
**Problem: No caching** Solution: Implement page caching, browser caching, CDN.
Waterfall analysis
The waterfall chart shows every asset being loaded and how long each request takes. Use this to identify bottlenecks: - Which assets take the longest? - Are there external scripts causing delays? - Are assets loaded in parallel?
Monitor over time
GTmetrix offers monitoring with historical data. This is valuable to see whether optimisations work and to detect performance degradation early.
WP Maintainer monitoring
We regularly perform GTmetrix analyses for our clients and proactively take measures on performance degradation. With our maintenance plan you do not have to worry — we ensure optimal performance.