BrowserMob Proxy (BMP) is based on technology developed in the Selenium open source project and a commercial load testing and monitoring service originally called BrowserMob and now part of Neustar.
The proxy is a free (Apache 2.0 license) utility that works well with Selenium or can be used independently.
It can capture performance data for web apps (via the HAR format), as well as manipulate browser behavior and traffic, such as whitelisting and blacklisting content, simulating network traffic and latency, and rewriting HTTP requests and responses.
For details and download: http://bmp.lightbody.net/ https://github.com/webmetrics/browsermob-proxy/downloads