The Firefox Profiler is a profiler that is built into Firefox. It has tighter integration with Firefox than external profilers. With its special annotations on Firefox's source code, it tells you what's happening at a point in time on your JavaScript code. With various measurements, it can provide more information and insight into your web application. During the talk, I will be briefly explaining the profilers, how to capture a good profile and how to analyze the profile data. I will be sharing Firefox Profiler specific features and how to make the best use of them. In the end of the slides, I will be doing a demo on how to analyze a performance problem. A profiler is a tool that monitors the execution of an application and gathers the data about the program execution in that time frame. Using a profiling tool to look at problems can make it a lot easier to figure out what’s going on in the application. It helps you to get detailed information about the execution of your application and it allows you to understand the behavior of it. At Mozilla, we are working hard to make the Firefox Profiler better for web developers. In Firefox, we are replacing the old performance panel inside the Developer Tools with Firefox Profiler so people can fully utilize all the new features that come with Firefox Profiler. We are both happy and excited to share more about this tool!