CLS Improvement Recommendations.
Background: CLS score is currently at 71% (Poor). Detailed analysis confirmed that the degradation occurs specifically in the Android WebView environment — primarily traffic coming from the Facebook in-app browser. Chrome, Safari, and Opera are unaffected because their browsers maintain a persistent font cache across sessions. Android WebView runs in an isolated process with no access to that shared cache, meaning Google Fonts are fetched from the network on every single visit. Combined with render-blocking scripts that delay font requests, users consistently see layout shifts before fonts arrive.
Two root causes were identified and confirmed via PerformanceObserver measurement.
