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Google PageSpeed Insights is a great free tool for testing Web Performance and checking Core Web Vitals. However, it lacks many advanced features such as a Waterfall Chart and the ability to select the test location and device.
Round Trip Time (RTT) is a metric that measures the time taken by a network packet to travel from sender to receiver and then back from receiver to sender.
RTT = Latency (Client to Server) + Server Processing Time + Latency (Server to Client)
AVIF and WebP are two modern image formats that offer a great level of compression and features when compared to older formats such as JPEG and PNG. If you want a newer format comparison, check our guide on AVIF vs JPEG-XL.
As of September 2025, both formats are widely supported, but WebP has an edge as according to caniuse.com, it has 95.29% Browser support compared to 93.8% of AVIF.
Are you looking for a Website Performance Testing Tool to replace GTMetrix?
Kashish Kumawat, the CEO of SpeedVitals was recently interviewed by Website Planet. The focus of the interview was to learn more about SpeedVitals and how SpeedVitals helps improve Web Performance. You can also read the original Introducing SpeedVitals announcement to see where the product started.