Stability and responsiveness is two major terms when the people talk about performance. With the help of performance testing, stability and responsiveness is checked of the application. JMeter is an open source performance testing tool, JMeter is designed to load test functional behavior and measure performance. To test performance on static and dynamic resources, Apache JMeter may be used. Such as files, web dynamic languages-PHP, Java, ASP.NET, Java, databases and queries, FTP services and more. This paper gives idea about the working of JMeter with an online web application, basically how to use JMeter to do the performance testing.