If you want to run a load test using real browsers, Flood Element is one of the best options. Element is a powerful open-source tool that you can use for both functional and nonfunctional testing. Here's how to get started.  

More about Element: http://bit.ly/3aMLcgZ 

Getting Started with Element: http://bit.ly/2W2oFZl

Run your first load test on Flood: http://bit.ly/2wK8buq