The original title is: "Using <link rel=preload> to reduce Blazor WASM LCP by 467ms"

Short summary

A Blazor WebAssembly site had a 3.5s LCP despite a 0.3s FCP because a 5.6KB JSON file sat at the end of a 43-file WASM critical request chain. Adding a single <link rel=preload> hint for that JSON file with as="fetch", fetchpriority="high", and crossorigin cut LCP by 467ms and element render delay by 97%. The post walks through the full diagnosis using PageSpeed Insights' network dependency tree and provides the exact three-line fix.

• •LCP was 3.5s because a tiny JSON file was fetched after all 43 WASM assemblies loaded
• •Adding <link rel=preload as="fetch" fetchpriority="high" crossorigin> cut LCP by 467ms
• •Element render delay dropped from 5,500ms to 180ms — a 97% improvement

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