Preserves a request’s original priority when it passes through a service worker. Previously, all requests going through a service worker would get "High" priority. This means render-blocking style sheets would have their priority clamped, while less-important resources would get boosted. The priority of network requests can be seen in the DevTools network tab. Render-blocking resources such as style sheets have "Highest" priority, while resources like async scripts have "Low" priority.
Explainers: N/A