Yellow Lab Tools is an open source project by Gaël Métais. It allows you to test a webpage (via an URL) and detects performance and front-end code quality issues.
This is done by loading the webpage via PhantomJS and collecting various metrics and statistics with the help of Phantomas. These metrics are categorized and transformed into scores. It also gives in-depth details so that developers can correct the detected issues.
By the way, it's free because I'm a geek, not a businessman. In return, you can add a ★ on GitHub. It will boost my motivation to add more awesome features!!!
<%if (sponsoring.about) { %>