JMeter is an open source tool and it’s used to measure the performance of any application under any predefined workload. It’s an Apache project.
JMeter is used by many organization because it can be run in distributed mode. And also as it’s open source, so it does not have any restriction on usage and distribution. And also JMeter has the test file format as JMX which can be easily imported in any commercial tools that is readily available in the market. And also the result is generated in JTL format which is very easy to import by any other third party tools.
That’s why it is the most commonly used tool for Performance Testing.