In performance testing as part of left shift we have to do frontend profiling along with server side performance testing. For frontend profiling i always recommend using https watch since it gives us great length of details for page rendering like css details, jss details, images, videos, and then the tool even shows how they are loaded.

This tool allows you to use a free version that can capture web traffic and analize it in real time whout the need of purchasing the full version that can give you a great idea of the product and test it before purchase the full version.

It was very easy to navigate and use for new people.