Selenium has become one of the most widely used automation tools today. Many tasks required for online testing are automated, including title checking, website navigation, link clicking, etc. Many developers already use the entire set of Selenium features, but few are aware of the ability to run tests in headless browsers. Even fewer people use this strategy in their daily testing. You can boost your testing performance to new heights with headless browser testing. Web browsers are an essential aspect of SeleniumWebDriver’s UI automation. Web automation testing requires the launch of a browser and then the execution of test cases on the browsers.

However, when we run Selenium tests on any browsers, we frequently encounter issues such as poor browser rendering, interference from other apps running on the system, etc. Apart from these, most of today’s CI systems are non-UI (such as Unix-based systems). Therefore, for executing the test cases on those systems, we require a way to run the different test cases in a Non-GUI mode. This is where the headless browser enters into the picture, which aids in the execution of Selenium.

1. Compared to actual UI testing, headless browser testing is often faster because it does not wait for the complete page to render before taking any action.
2. The test can be done even if the system has no real browser installed.
3. In parallel testing, if numerous sessions are launched simultaneously, the testing can be completed without the requirement for human interaction. Similarly, the user can work on multiple projects at the same time.
4. Only a few Headless Browsers support screenshots, such as Chrome and Firefox.
5. For Selenium script debugging, we can temporarily turn off the headless mode in Chrome and Firefox.

Headless testing is possible with Selenium. We mostly used the HTMLUnitDriver in prior Selenium versions, a headless driver that provides a non-GUI implementation of Selenium WebDriver. Selenium now supports headless versions of actual browsers like Chrome, Firefox, and Edge in the latest versions of SeleniumWebDriver 3 and Selenium Webdriver 4. In addition, selenium provides several options for running these browsers in headless mode.

The following are the advantages of running a Selenium test case in headless mode:

1. It is not always practical to install real browsers on distant workstations when we need to run automated test cases remotely on a server or build and release pipelines for continuous integration servers. Instead, we can use headless browsers to execute automation tests efficiently.
2. When running Selenium tests, you’ll need a computer to handle the web browser’s visuals. We can eliminate this requirement and test in a broader range of devices with headless testing—servers, Docker containers, etc.
3. Headless browsers are an excellent alternative when writing a web scraper or data extractor that has to visit websites and collect data. We see web pages and obtain data since we are not concerned with functionality in these circumstances.
4. The tester may repeatedly want to emulate multiple browser versions on the same computer. You should utilize a headless browser in that scenario, as most allow you to simulate several browser versions.
5. Compared to real browser automation, the performance of a headless browser is superior. Loading CSS, JavaScript, Images, and opening and rendering HTML takes a long time in genuine browsers like Google Chrome, Firefox, and Internet Explorer. Headless browsers don’t need all of this to load and can begin executing tasks without waiting for a page to load fully. We could save time by running regression scripts in headless browsers when we need to run them.
6. You can use headless browsers for multitasking. While the tests are operating in the background, you can do whatever else with your browser or computer. We can save hours by not gazing at the screen.

Headless Chrome is a technique to operate the Chrome browser without the complete user interface in a headless environment. Headless Chrome gives you a real browser experience without the memory drain of running the full version of Chrome. Since version 59, Google Chrome has supported headless execution. Selenium WebDriver has a class called “ChromeOptions” that allows you to customize Chrome’s default behaviour by specifying various options. One of these options is the “headless” mode, which runs the test cases when Chrome is in headless mode. The following code snippet demonstrates how to use the ChromeOptions class to pass the “headless” option.