Glossary term
What is TBT (Total Blocking Time)?
TBT stands for Total Blocking Time.
A lab number: the total time long tasks blocked the main thread. Lighthouse uses it as a stand-in for INP.
Learn it properly · The Browser ContractLesson 9: Core Web Vitals for Engineers: LCP, INP and CLSWhat each metric measures, its “good” limit at the 75th percentile, why INP replaced FID, and the difference between field data and lab data.