HTML / XML / JS, low-level validity (cross-cutting)MediumInferred
Render-blocking synchronous JS in head
What it is
Blocking scripts delay render.
Why it matters
Slows paint/LCP.
How to fix it
Defer/async non-critical JS.
Impact
Low-medium. Inferred.
Evidence
Reduce render-blocking JS. web.dev, Core Web Vitals (Google); Google Search Central, Understanding page experience in Google Search results
Sources