At SpeedCurve, we're fond of the phrase "a joyous user experience". Creating this joy requires delivering what users want as quickly as possible. It's important that the critical content is downloaded and rendered before users get frustrated. Network metrics have been around for decades, but rendering metrics are newer. Speed Index. Start Render. Time to First Interactive. First Meaningful Paint.
![SpeedCurve | Evaluating rendering metrics](https://cdn-ak-scissors.b.st-hatena.com/image/square/55effa72671ae4d2e608462a388588b477b418c2/height=288;version=1;width=512/https%3A%2F%2Fblog-img.speedcurve.com%2Fsocial%2Frendering-picker.png%3Fauto%3Dformat%2Ccompress%26fit%3Dcrop%26ar%3D2%3A1%26w%3D1200)