What is a Headless Browser?

Apr-05-20225 mins read

The software development life cycle keeps coming up with new techniques to decrease delivery time and ends in testing to ensure quality product deliverables at reduced cost and effort. Testing the web applications is trickiest as the tester must test applications on different browsers. This is difficult because there are numerous browsers available in the

The software development life cycle keeps coming up with new techniques to decrease delivery time and ends in testing to ensure quality product deliverables at reduced cost and effort. Testing the web applications is trickiest as the tester must test applications on different browsers. This is difficult because there are numerous browsers available in the market and it is difficult to know which browser a user might utilize.

The tester must ensure that the web application does not have issues in integration, usability, User Interface(UI), interoperability, and security. Headless browser testing makes the testing of web applications easier.

What is a Headless Browser?

A headless browser is a web browser or software that accesses web pages to provide results without any identifiable graphical user interface. Users may not see the results, and the content is passed on to other programs to test web pages for quality control or to extract data.

Website development continues to evolve And developers work to find out new ways to build a user interface that engages their customers to deliver an optimal user experience to website visitors. 

Developers are concerned themselves with the aesthetics of a web page and incorporate more interactive elements on their websites. Headless browsers access a web page to determine how much space it would occupy when the user views it.

Headless browsers help the tester view other elements that would appear for a user, such as the color, the font size of the text, and the x/y coordinates of an object, which create a seamless browsing experience for the user.

What is the need for a headless browser?

A headless browser understands web pages like a traditional browser and must parse JavaScript, click on links,  and manage downloads. According to Google, headless browsers could help the search engine to cope with AJAX web sites. AJAX is a technique that creates dynamic web pages quickly and updates them without reloading the webpage.

When the search engine requests a web page, the headless browser must access the AJAX website on the server and provide the results with its program. 

Google expects website owners or administrators to set up a headless browser on the webserver rather than on a client machine. When using the headless browser, the website administrators may parse the JavaScript instead of the search engine. Google proposed a set of protocols that tells the search engine when to request the headless browser for information and which URL to show to the user. This paves the way for administrators to see what Google’s spider bots see in the search results.

What are the uses of a headless browser?

Headless browsers can understand HTML pages and interpret elements such as colors, fonts, and layouts. Users utilize headless browsers for web page testing to check for automation, layouts, performance, and for data extraction.


Automation tests check for submission forms, mouse clicks, and keyboard inputs while testing automatic elements to save time and effort in any part of the software delivery cycle. 

Layout Testing

Headless browsers render and interpret HTML and CSS elements like a real browser. They check the layouts to determine the default page width, their elements, and their x and y coordinates. 


Headless browsers test web page performance since it does not have a graphic user interface(GUI) and loads much faster. It does not require any User Interface(UI) interaction and you may do the testing from the command line itself. 

Data Extraction

Data extraction is easy as it does not need to load the webpage and can navigate websites to collect public data.

Automated UI tests

Tests the webpages for proper navigation until the transaction completes, but if a website fails, it might cause a bad review of the website, hampering its success.

Popular Headless Browsers

Headless browsers allow you to execute every use case necessary to simulate the actions of target users. 

Mozilla Firefox

Mozilla Firefox is a headless browser that can connect to different APIs. Selenium framework is mostly used with headless Firefox for performing automated tests. It’s a relief for developers to simulate different browsers to test their websites. They can easily connect to different APIs to run Firefox in headless mode and test different use cases.

Google Chrome

Chrome browser runs in a headless environment using Headless Chrome without the full browser UI. The key benefit is that JavaScript executes in the same environment as users of your site which prevents a memory overload of running the full version of Chrome.

Puppeteer framework tests Headless Chrome using JavaScript commands by creating an automated test environment to run tests directly on the latest version of Chrome using JavaScript.


HtmlUnit is a headless web browser written in Java to parse the HTML of a site. It interacts as a normal user does through a browser, checks JavaScript and CSS syntax, submits forms, and parses responses to see the content of its HTML elements. It focuses on testing e-commerce websites for testing submission forms, website redirects, and HTTP authentication.


PhantomJS handles complex internet design using command line testing. This headless Webkit is scriptable via the JavaScript API and uses CasperJS for testing. CasperJS is an open-source navigation scripting and testing tool written in JavaScript for the PhantomJS WebKit headless browser.

PhantomJS may simulate the navigation scenario that reveals the places where a user might encounter errors while browsing.


TrifleJS is a headless browser for Internet Explorer using the .NET Web Browser Class with a Javascript API. It is an executable file instead of an SDK or API and its code functions as a port of PhantomJS. 

Advantages of headless browsers

  • Headless browsers work with Linux OS without GUI and are executable via the command-line interface.
  • Used when there is no need to view anything and ensures that all tests are successful.
  • Parallel tests can be conducted using headless browsers as they don’t consume a lot of memory and resources.
  • They are useful when you wish to simulate multiple browsers on a single machine or run test cases for creating data.
  • When compared to real browsers, headless browsers are faster.

Disadvantages of headless browsers

  • Since they load fast, they are difficult to debug.
  • Real browser tests include performing test cases with GUI. Special cases where you must perform test cases with GUI, are where you cannot use headless browsers.
  • When an error occurs, it is difficult to report them with the help of screenshots.  A traditional browser presents the defects by generating screenshots that cannot be expected in a headless browser.

Selenium Headless Browser Testing

The majority of the Continuous Integration(CI) systems are Unix-based systems that are Non-UI and require test cases to run in a non-UI mode. Headless browsers help in the execution of the Selenium Headless Browser tests in a non-UI mode.

Selenium is a free, open-source testing tool that performs automation tests. It allows writing scripts in languages like Java, Python, C#, Ruby, Perl, and Scala, supports browsers like Firefox, Chrome, Internet Explorer, Opera, and Safari, and is capable of running on Windows, Linux, and macOS.

Selenium Webdriver supports dynamic web pages where various web elements change without loading the page. The integral part of UI testing is web browser testing.  Web automation tools launch the browser and then execute the test cases on it. 

When you run the Selenium tests, browsers face some challenges like slow rendering of headless browsers and the interference of other applications running on the system.

Frequently Asked Questions

1. Why is it called a headless browser?

Headless browsers do not have a graphical user interface (GUI) and it provides automatic control of a web page. Users execute headless browsers through the command-line interface or through network communication and are useful for testing web pages as they can understand the HTML tags in the same way a regular browser does.

2. What is the use of headless browser testing?

Headless testing is running browser UI tests without the head, which means without any browser UI. This is useful in a continuous integration environment to test the web pages since there is no need to load the extra overhead of the browser GUI.

3. What are the limitations of headless browser testing?

Though headless browsers are easy to be test, users might encounter bugs when they use them in real-time. The best way to test for user experience is for the developer to mimic a real user and perform a functional test. 

The headless browser testing would throw and catch bugs that could not happen in a regular browser. 

Final Thoughts

Due to their speed and agility, headless browsers are best for web page testing because they test the various automation tasks, their performance, and layout on a website. 

Headless browsers also work for scraping websites faster as they do not deal with the overhead of loading any UI and can automate the scrapping mechanism to extract data in an optimized manner.

ProxyScrape offers flexible plans for you to choose from for scraping websites. Keep visiting our blogs to learn more about proxies and their various applications.