Code

Avoid chaining critical requests

To optimize website performance and loading speed, a Code/Performance audit is essential to prevent the chaining of critical requests, which can significantly impact a user's browsing experience by causing delays in rendering important content."

Critical request chains are series of dependent network requests important for page rendering. The greater the length of the chains and the larger the download sizes, the more significant the impact on page load performance.

Sitefig reports critical requests loaded with a high priority:

A screenshot of the Lighthouse Minimize critical request depth audit

How Lighthouse identifies critical request chains

Lighthouse uses network priority as a proxy for identifying render-blocking critical resources. See Google's Chrome Resource Priorities and Scheduling for more information about how Chrome defines these priorities.

Data on critical request chains, resource sizes, and time spent downloading resources is extracted from the Chrome Remote Debugging Protocol.

How to reduce the effect of critical request chains on performance

Use the critical request chains audit results to target the resources that have the biggest effect on page load first:

Minimize the number of critical resources: eliminate them, defer their download, mark them as async, and so on.
Optimize the number of critical bytes to reduce the download time (number of round trips).
Optimize the order in which the remaining critical resources are loaded: download all critical assets as early as possible to shorten the critical path length.