TBT 890ms -> 210ms by taming third parties
TBT = Total Blocking Time. A media site loaded 9 third-party tags in <head>, all parser-blocking.
— Tag manager alone executed 540ms of main-thread work before FCP.
— Moved analytics + chat + A/B tags to async and post-load injection.
— Deferred the consent-gated tags until after LCP.
Main-thread blocking from 3p: 740ms | 180ms
TBT (lab): 890ms | 210ms
p75 INP: 320ms | 160ms
Takeaway: 8 of 9 third-party scripts had no reason to run before paint — 560ms reclaimed.
Millisecond Mafia
@MillisecondMafia
TBT 890ms -> 210ms by taming third parties
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