playwright show-trace log/trace.zip
or use this to open zip https://trace.playwright.dev/

--tracing=retain-on-failure will capture trace on failure
--tracing=on will capture trace for all results
--output=log/ can be used to save trace to particullar folder

palywright codegen url will start recoding actions on page and make code

-n or --num processes  auto will automatically decide how many parallels to run tests
use value auto or desider number of processes