Total Blocking Time (TBT) is a load responsiveness metric that measures the usability of the web page during the loading. Total Blocking Time is an important user-centric performance metric that compares the time amount of non-responsive and responsive time during the rendering phase of the web page.
1.1 Identification LCP
Tools like Page speed insights,GTMetrix,lighthouse.
1.2 TBT Audits Tool
Reduce the impact of third party code
Minimize main-thread work
Avoid an executive DOM size
Avoid long main thread tasks
Note: If TBT is optimized, load-responsiveness will be better and First Input Delay.