I am having problems understanding Selenium Grid even after watching YouTube videos. Also, is it true that not every Selenium tester should know it.

Earlier I also had problems understanding Maven, but after experts explained it to me, things got a lot clearer and videos made a lot more sense. So please help me to understand what Selenium Grid is needed for, so that maybe after I watch YouTube videos again I can grasp it better.


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Selenium Grid

Selenium Grid is a server that allows tests to use web browser instances running on remote machines.

With Selenium Grid, one server acts as the hub. Tests contact the hub to obtain access to browser instances. The hub has a list of servers that provide access to browser instances (WebDriver nodes), and lets tests use these instances.

Selenium Grid allows running tests in parallel on multiple machines, and to manage different browser versions and browser configurations centrally (instead of in each individual test).

The ability to run tests on remote browser instances is useful to spread the load of testing across several machines, and to run tests in browsers running on different platforms or operating systems. The latter is particularly useful in cases where not all browsers to be used for testing can run on the same platform.

Whether you should know about Selenium Grid is dependent on your current task.

Read it more here. Link to Selenium Grid Documentation


Assume that you're working on a project that requires testing on multiple configurations. What are you going to do? Running different scripts on each and every device is cumbersome. Automation Testing will help you save time and manual efforts. As an automation tester, you should know about Selenium grid.

This is exactly why Selenium Grid is built. It can help you test on all major browsers, all major operating systems, and even on mobile device browsers. You can get a huge browser coverage in all your functional tests ensuring the perfect experience for a wide range of your potential users.

What Is Selenium Grid?

Selenium Grid allows parallel testing against various browsers & OS combinations through a Client-Server model. Here, the Server is known as the Hub which has multiple Clients to interact with. With Selenium Grid, you can connect a server to multiple remote machines which can then be used to run a browser automation script over multiple browsers + OS configurations, simultaneously.

How Selenium Grid Works?

Selenium Grid is comprised of two concepts:

Hub: It is the center of the Selenium Grid architecture that manages the network of the test machines. There is only one hub in a network that is assigned to a test of Desired Capabilities(operating system, browser, browser versions) and then the hub finds the test that matches the given configurations. A Selenium Hub is referred to as the server.

Nodes: Nodes are the test machines that execute the test that was earlier loaded on the hub. There can be multiple nodes configured with a different operating system and different browsers. It is not mandatory for the node to run on the same platform on which the hub is running. Selenium nodes are referred to as clients connected to a server.

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How to Configure Selenium Grid?

  1. Ensure that your system has Java Runtime Environment (JRE) or better yet Java Development Kit (JDK) installed. Though most people recommend going for the latest JDK, I prefer earlier tried and tested versions like JDK SE 08 or 09. You can go for the latest one if you wish.
  2. Download and extract Selenium Standalone server JAR files from here.

If you are willing to learn Selenium Grid from scratch, then check out this Selenium Grid tutorial.

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