What is one important aspect to ensure when using the Speed index metric?

The Speed Index metric is specifically designed to measure how quickly contents become visually populated on the screen during page load, allowing a focus on the perceived load time from the user's perspective. It is particularly relevant for actions that involve loading new content or refreshing parts of a page, as this metric quantifies how fast a user sees visual results after initiating a request.

This emphasis on load actions is fundamental because Speed Index directly relates to user experience during page transitions or interactions that trigger content changes. Hence, utilizing it solely for load actions captures the intent and utility of this metric effectively. By concentrating on instances where content is loaded, it provides a useful indicator of performance tailored to the actions resulting in dynamic content changes—ensuring effective feedback on how quickly users perceive the availability of visual information.