Headless Browser: What Is It And How Does It Work?

A headless browser is, in brief, a web browser lacking a graphical user interface (GUI). The user interface consists of digital elements with which the user interacts, such as buttons, icons, and windows. However, there is much more to learn about headless browsers.

This article explains what a headless browser is, what it is used for, what headless Chrome is, and which other headless browsers are the most popular. We will also explore headless browser testing’s key constraints.


Understanding A Headless Browser

A headless browser is one that lacks a graphical user interface (GUI). It is mainly used by software test engineers since browsers without a graphical user interface are more efficient because they do not need to render visual content. The ability of headless browsers to function on servers without GUI support is one of their most important advantages.


Typically, headless browsers are executed via the command line or network connectivity.


What Is A Headless Browser For?

Web page testing is the most popular use case for headless browsers. Headless browsers comprehend and interpret HTML pages as well as any other browser. They represent style components, such as colors, typefaces, and layouts.

So, what use does headless browser testing serve?



In order to test submission forms, keyboard inputs, mouse clicks, etc., headless browsers are utilized in automation tests. It encompasses everything that can be automated to reduce time and effort in any phase of the software delivery cycle, such as development, quality assurance, and installation. JavaScript libraries are likewise subject to automated testing.


Layout Testing

Headless browsers are able to render and comprehend HTML and CSS elements identically to conventional browsers. They are utilized for layout validation, such as determining the default page width and element locations. Headless browsers also permit testing of color selection for various elements. Additionally, JavaScript and AJAX execution can be examined. To verify the layout, developers frequently automate screen grabs in headless browsers.



Using a headless browser, website performance may be evaluated fast. Due to the fact that a browser without a graphical user interface loads websites significantly faster, performance activities that do not require UI interaction can be tested via the command line. In such situations, it is unnecessary to reload pages manually. While this saves time and effort, it is crucial to highlight that a headless browser can only be used to investigate modest performance activities, such as login tests.


Data Extraction

When using a headless browser for web scraping and data extraction, it is often unnecessary to launch a website. Web scraping with a headless browser permits rapid website navigation and data collection.


Most Commonly Used Headless Browsers

One of the most important needs for headless browsers is the ability to operate with few resources. The browser should operate in the background without significantly delaying the performance of other system functions.

In certain testing conditions, different headless browsers perform better. In order to determine the optimal combination of tools for a given project, developers must frequently try a variety of possibilities. Here are some of the most well-known headless browsers and their primary characteristics:


  • Google Chrome – It may operate in a headless environment and provide a standard browser context while consuming less RAM. The headless mode of Google Chrome is available in versions 59 and beyond. Headless Chrome’s most typical uses include printing the Document Object Model (DOM), producing PDFs, and capturing screenshots.
  • Mozilla Firefox – In headless mode, it is compatible with several APIs. Selenium is the most common framework for usage with Firefox. Headless Firefox is typically used for running automated tests since it improves testing efficiency.
  • HtmlUnit – This is written in Java and is utilized to automate various user interactions with websites. This headless web browser is widely used to test e-commerce websites since it is ideal for testing submission forms, website redirects, and HTTP authentication.
  • Phantom JS – It is also noteworthy because it was formerly a prominent headless web browser. Numerous developers have contrasted PhantomJS to HtmlUnit. Nevertheless, Phantom JS has been retired for several years. It was open-source and sponsored by developer contributions.


Final Words

Headless browsers are significantly faster than conventional browsers since they do not need to load all the content that adds to the user experience.


Due to their speed, headless browsers are frequently used for testing web pages. They are deployed to test a website’s performance, layout, and numerous automation activities. Another prominent use case for headless browsers is data extraction.

The headless mode is supported by some of the most popular web browsers, including Chrome and Mozilla Firefox.

However, headless browsers also have limits, and testing should, in some situations, be undertaken on conventional browsers. Read more of our blogs here at The Social Proxy.

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