Back Forward Cache is a technique browsers use to instantly load a Web Page when the Back or Forward buttons on the browsers are pressed.

Back/Forward Cache is currently supported by all major browsers including Google Chrome, Mozilla Firefox, and Safari. According to Google Chrome's data, about 10% of all navigations on Desktop are either Back or Forward. This number goes all the way to 20% in the case of Mobile browsing.

By ensuring that your website is eligible for Back/Forward Cache, you can make a dramatic difference to the Page Speed and User Experience of your website. It can also complement other stability work such as fixing layout shift during normal page loads.

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?