Exploring Headless Browser Testing with Selenium

When it comes to web development, developers use popular browsers to test their applications and ensure they work smoothly for users. The most popular browsers among testers and quality assurance are Chrome, Firefox, and Microsoft Edge.  Opera, Brave, and Safari browsers online also make the list. The resource-intensive GUIs of these modern browsers are why “Headless Browser,” a free alternative, was created.

A Headless Browser executes scripts without a GUI. A headless browser is a browser that communicates programmatically with websites rather than presenting content in a visible browser. Developers and testers can automate non-GUI tasks such as web scraping and automated testing.

Here, you will learn the importance of headless web browsers, selenium testing on headless browsers, and their benefits and drawbacks. It also explores best practices for headless browser testing.

What is a Headless Browser?

A Headless Browser is a web browser without a GUI (graphical user interface); in simple terms, a browser without a user interface or window. A Selenium headless web browser works in the background to process API requests or responses from web pages.

In contrast to traditional web browsers, headless browsers allow automated tests to be run and web scraping to take place without the user having to interact. These browsers are especially useful for web developers or testers who must automate repetitive web page tasks or test web applications.

Selenium headless web browsers are used like conventional browsers to interact and modify web pages, run JavaScript, and change HTML elements.

What is Headless Browser Testing?

Headless browser testing involves testing web applications with a Selenium headless browser, which does not have a graphical interface. Headless browser Selenium runs in the background without rendering a user interface. This allows developers and testers to automate web testing while reducing the need for manual tests.

Selenium headless testing is writing automated test scripts to mimic user behavior. These scripts can test multiple things, including a website’s functionality and user interface elements. These scripts are run using a headless Selenium browser. Web developers and testers can ensure that their web applications work properly in various environments and platforms using headless browser tests.

Why Headless Browser Testing is Important?

It is essential to use headless execution because it allows testers and developers to run automated tests without the need for a graphical interface. It is important to note that the user interface of conventional browsers can hinder testing and consume a large amount of system resources. On the other hand, headless browsers can run tests faster and more efficiently without an interface.

Headless execution is also crucial because it facilitates the workflow of CI/CD (continuous integration and continuous delivery). In modern software development, releasing code changes quickly and confidently is important. Headless testing makes integrating automated tests into the CI/CD process easier.

Headless implementation can also reduce costs for testing and development. Selenium Headless Browsers can run on lower-powered machines or virtualized environments to minimize the need for expensive equipment. It can help organizations save money and resources by making testing and deploying web applications easier.

Headless Browser Testing with Selenium

You can run Selenium in headless mode using several methods. This section will cover three ways to run Selenium tests headless: the HTMLUnitDriver, Headless Chrome, and Headless Firefox.

1) HTMLUnitDriver: Running Selenium headless browser tests

Step 1: Vist the official website of Selenium and download Selenium WebDriver for Java

Step 2: Download the HTMLUnitDriver from the HTMLUnit website.

Step 3: In your project, you must add these JAR files: “Selenium WebDriver and HTMLUnitDriver.”

Step 4: In Selenium code, create a new instance of the HTMLUnitDriver.

Step 5: Write your Selenium test code and run it using HTMLUnitDriver.

2) Chrome: Running Selenium Headless Test

Headless Chrome can be used to run Selenium tests headless. How to use Selenium Headless Browser Chrome for Selenium testing:

Step 1: Download and install ChromeDriver.

Step 2: Add the path of ChromeDriver to PATH in your system environment variables.

Step 3: Create a ChromeDriver instance in your Selenium code.

ChromeOptions options = new ChromeOptions();


WebDriver driver = new ChromeDriver(options);

Step 4: Set option.setHeadless() as shown in the code above.

Step 5: Use the ChromeDriver to write and execute your Selenium code.

3) Running Selenium tests for Headless Firefox

Headless Firefox can be used to run Selenium tests headless. How to use Headless Firefox for Selenium testing:

Step 1: Install the latest version.

Step 2: Add the path of geckodriver into your system’s environment variable PATH.

Step 3: Create a new FirefoxDriver instance in your Selenium code.

FirefoxOptions options = new FirefoxOptions();


WebDriver driver = new FirefoxDriver(options);

Step 4: Set option.setHeadless() as shown in the code above.

Step 5: Use the FirefoxDriver to write and execute your Selenium code.

4) Testing Headless Edge with Selenium

Headless Edge is a Selenium headless web browser that allows you to run Selenium tests headless. How to use Headless Edge for Selenium testing:

Step 1: Install the latest Microsoft Edge Driver.

Step 2: Add the path of Microsoft Edge Driver to PATH in your system environment variables.

Step 3: Create a new EdgeDriver instance in your Selenium code.

EdgeOptions options = new EdgeOptions();

options.setCapability(“ms:edgeOptions”, “{\”headless\”:true}”);

WebDriver driver = new EdgeDriver(options);

Step 4: Set the headless flag in the option.setCapability() to true as shown in the code above

Step 5: EdgeDriver allows you to write and execute your Selenium code.

5) Testing Headless on Selenium Cloud Grid

Testing Headless Browsers on Cloud Grid LambdaTest allows you to test web applications across multiple browsers and operating systems without worrying about maintaining or setting up your infrastructure. This section will cover the Selenium Framework.

Follow these simple steps before running a Python Test on LambdaTest.

Step 1: Create a LambdaTest Account and complete the necessary processes.

Step 2: Visit the LambdaTest Dashboard. Navigate to your profile avatar at the top-right corner.

Step 3: Select Account Settings to redirect you to your profile.

Step 4: Go to Security & Password. Save your Username Access Key for future use.

Benefits of Headless Browser Testing with Selenium

Selenium headless testing has many advantages: speed, cost-effectiveness, and scalability.

  • Speed: One of the major advantages of Selenium headless browser execution is its speed. Testing and scraping websites can be very difficult when conventional browsers render the user interface. On the other hand, the headless browser Selenium testing can perform better because it does not have to render the user’s interface. This allows faster and more efficient execution of automated testing and web scraping, saving time and resources.
  • Scalability: Scalability is a key advantage of headless browser execution. Because they run in the background, headless browser Selenium is easily scalable to run on multiple computers or the cloud. This allows you to run large-scale automated testing or web scraping without buying expensive hardware.
  • Platform Independent: Selenium can be run on any operating system, including Windows and macOS. It eliminates the worry of compatibility issues when testing web applications in different settings and platforms. Selenium headless browsers don’t need a graphical interface. They can, therefore, be used on devices with fewer capabilities or in virtualized environments. This can save resources and money.
  • Cost-Effective: Cost savings can be achieved by developers and testers using headless browsers. Selenium headless web browsers can help developers and testers save money by reducing hardware costs. Selenium headless web browsers can be used on devices with lower capabilities or in virtualized environments, saving hardware costs.
  • Continuous Integration: Selenium headless web browsers are included in workflows for continuous integration (CI/CD). Automating tests using the headless Selenium browser allows developers to ensure that code changes will not impact existing functionality. The headless browser Selenium is a great way to automate tests and ensure that code changes are only deployed after they pass the tests.

Selenium Headless Testing Limitations

Selenium headless testing has many benefits but also certain limitations. These limitations include:

  • Limited Support for GUI-related Testing: Since the headless browser Selenium does not support GUI testing, certain tests, such as those that check for visual regression or require user interaction, can’t be run in headless.
  • Difficulty Debugging: Debugging in headless mode is more difficult because there is no visual interface to show the content or error messages. Developers may use logging tools and other debugging techniques to find issues.
  • Limited Browser Compatibility: Some older browsers or less popular browsers may not offer this mode. This can restrict the testing scope, especially when the web application is to be tested on multiple browsers.
  • Inconsistent Rendering: Selenium, the headless web browser, may not render pages the same as other browsers. It can cause inconsistencies in how web pages or elements are styled or positioned.
  • Limited JavaScript Support: JavaScript is not supported by all headless browsers. This can harm the functionality of web applications that heavily rely on JavaScript. This can lead to false negatives in automated tests or inaccurate results.
  • Difficulty setting up: Headless mode is more complicated than traditional browser mode. Headless mode requires additional setups, like configuring a display or installing specific browser drivers.
  • Security Concerns: Using headless browsers in illegal activities such as web scraping and botnet attacks is possible. These browsers can cause massive data leaks. This may cause security concerns for website owners and developers. To protect against such attacks, they may have to implement additional security measures.

Headless Browser Testing Best Practices

You can optimize your headless browser testing process by following best practices. This will ensure you can provide reliable, effective, and maintainable tests. Here are some recommended essential practices to take into consideration:

  • Implement Page Object Model: Using Selenium or similar frameworks to create reusable test code. POM separates the test logic from page-specific details. This makes tests more robust.
  • Use assertions wisely: Implement explicit and informative statements to verify expected behaviors in your tests. Use descriptive error messages to aid debugging. Use a reasonable amount of assertions to avoid making tests fragile.
  • Handle Asynchronous Operation: Web applications frequently involve asynchronous operation. Tests should be able to wait for data to load or AJAX requests. Use explicit waits or the built-in mechanisms of your testing framework.
  • Monitor test performance: Monitor your headless browser testing, including the execution time and resource usage. As needed, address performance bottlenecks. Use profiling tools to identify resource-intensive or slow test cases.

End Note

A Selenium headless web browser is one that does not have a graphical interface. Selenium Headless Browser Testing is a form of automated testing that runs tests using a headless web browser. Selenium tests may be run headless using a variety of drivers, including HTMLUnitDriver and Headless Chrome, Headless Firefox, and Headless Edge.

Headless execution allows for faster and more efficient testing. It supports CI/CD workflows and enables testing on multiple platforms and environments. Selenium headless tests have limitations, including limited GUI support, inconsistency in rendering, limited JavaScript, incompatibility with certain browsers, difficulties in debugging, and security concerns.

The decision to use the headless mode in web development or testing depends on the requirements of the project and the tradeoffs between the benefits and limitations.