Headless Browser Testing: Should You Consider This?

What is Headless Testing?

Headless testing is a method for evaluating a website’s or online application’s functionality without having to use a web browser. The test script simulates operations like clicking buttons and filling out form fields by sending commands directly to the website’s source code rather than engaging with it through the UI. As a result, testing may be done more quickly and effectively because there is no need to load a full web browser; the test script can instead run in the background.

Advantages of Headless Testing

Headless testing has many advantages. Here are some:

  • Speed of Execution: Headless tests run substantially quicker than tests executed on a real browser. The primary reason for this is that your tests aren’t having to start up a browser UI each time. This means they can avoid the time it takes a real browser to load JavaScript, CSS, and render HTML on a website. I’ve seen estimated execution time savings in the range of 7-15%.
  • CICD: Because its so much quicker, it makes it ideal for continuous integration and delivery (CI/CD) pipelines.
  • Server Testing: It can also be helpful for testing web applications in contexts without a UI, such as servers.
  • Multi-Tasking: The test script can run in the background and finish tests more rapidly because it does not need to open a full web browser.
  • Shift-Left: Because it runs so much quicker than real browser testing, you can get results of your testing much faster.

Disadvantages of Headless Testing

Headless testing has some potential disadvantages, though. Here are some:

  • User Experience: Headless testing may not always correctly imitate the user experience, which is one potential problem. The test script may not always correctly reflect how a user would actually interact with the website or web application because it is engaging directly with the source code rather than through a UI.
  • UX or Visual Design: Additionally, headless testing might not be able to completely test specific features of a website or web application, including the user interface or visual design.
  • Debugging: Debugging with headless can be challenging. Typically you will need to run the traditional way to get to the bottom of failures.
  • Real-time test execution visual: When running headless you don’t get the option to watch your test running on the UI.

Headless Testing Use Cases

There are certainly times when headless testing can add value to your test strategy. Here are some:

  • Simulating multiple browsers on a single machine
  • Running tests on a headless system without a UI
  • Element testing – since headless browsers render and interpret CSS & HTML like a real browser, you can use them to test style elements such as buttons, forms, links, etc…
  • Extracting values from a page / scraping
  • Extracting a PDF
  • Generate test data
  • Performance issues such as SSL, front- and back-end code, and load considerations, as well as non-graphic elements such as response time, error handling, and access to remote resources, can all be evaluated using headless testing.

Common Headless Browsers

For headless testing, a number of tools and frameworks are available, including Headless Chrome, PhantomJS, and HtmlUnit, Firefox, Puppeteer, and Splinter. These tools allow you to create and execute test scripts in a number of different computer languages, such as Java, Python, and JavaScript.


In general, headless testing is a helpful tool for speeding up your automation testing suite. In CI/CD pipelines, where it helps speed up build times and guarantee the quality of the finished output, it can be especially helpful. However, as with anything, this shouldn’t be your only solution to speeding up tests. Things such as test grids, or paralyzing your test executions, should be considered in your strategy. To guarantee a thorough testing strategy, it’s crucial to carefully analyze the headless testing restrictions and advantages and apply it in conjunction with other testing techniques.

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