In JMeter, controllers are used to regulating the flow of request execution. They allow you to specify the order in which requests are processed in a Thread. It allows you to choose "when" a user request is sent to a web server. They choose the sequence in which user requests are processed.

Some controllers used in JMeter are listed below :

* Recording controller :- JMeter has the ability to record your testing steps; a recording controller is a container for these recordings.

* IF controller : IF Controller decides whether or not to run a batch of child samplers based on particular criteria.

* While controller : The JMeter While Controller basically runs child Samplers and keeps running until the condition in the condition field becomes false.

* Transaction controller : The Transaction Controller in JMeter is a useful tool for organising and determining how different pieces of your test will appear in a report. The Transaction Controller creates a second sample that measures the total time it takes to complete the nested test items.
* Loop controller : The Loop Controller causes the user request to be repeated a given number of times or to be repeated indefinitely.

* Simple controller : Simple Controller is a container for user requests.

* Module controller : Module Controller's purpose is to make JMeter more modular. Web applications, in general, are made up of small functional units (e.g., login, create account, logoff...). This capability can be saved as "modules" in Simple Controller. The Module Controller will determine which module is required to run.

* Random Controller : In each loop period, the Random Controller causes all user requests to be processed in a random sequence.

* Interleave Controller : Interleave Controller takes one of the user requests and makes it run in each loop of the thread.