Site Speed Optimization Contributed Factors
- Test Location
- Recommendations
- Time to Stop Test (Onload Time, Fully Loaded Time)
- Real Browsers vs Headless/Emulated Browser
- Other Features (Connection Throttling, HTTP/2 Support, Screen Resolution, Hardware Provision)
Which tool should I use?
- Quick Checks: GTmetrix, Pingdom Tools, and PageSpeed Insights
- Consistency/Historical Tracking GTmetrix and WebPagetest
- In-depth Analysis: GTmetrix and WebPagetest
- SEO Check: PageSpeed Insights, GTmetrix, and Pingdom Tools
- Mobile Devices: WebPagetest, GTmetrix, and PageSpeed Insights
- Location Dependent: WebPagetest, GTmetrix, and Pingdom Tools
- Advanced Options: WebPagetest and GTmetrix
Source: https://gtmetrix.com/blog/the-difference-between-gtmetrix-pagespeed-insights-pingdom-tools-and-webpagetest/