What Is a Headless Browser and How Is It Used?

Usually, a standard GUI (Graphical User Interface) browser with tabs of websites and buttons is sufficient to access a website. However, for web application testing, data collection from hundreds of pages, or execution of scripts, the interface can hinder functioning. In these scenarios, resource inefficiency and automation issues arise. So, one might ask, what is a headless browser?

Functionally, it doesn't differ from traditional ones. The striking difference, however, is the absence of an interface. It can do everything that regular ones can, but it operates in the background and much faster.

In this article, we'll explain their structures, discuss application areas, offer guidance on selecting suitable tools for various tasks from testing to scraping, and outline critical considerations for avoiding blocks.

What is a Headless Browser?

Before explaining how a headless web browser works, it’s important to note that they are two types – true and virtual.

In such browser architecture without visualization or a graphical user interface, the data processing occurs directly in the device’s memory.

In the second case, a frame buffer simulation is used. It acts as a stand-alone display, featuring standard interface building blocks, and simulates a screen display from which the browser interacts with the device.

The first option is usually used: lighter, faster, and easier to configure.

Initially, the term headless might appear to mean “cut down”. Indeed, there are no windows opened, pages are not displayed on a monitor, and a mouse is not needed. So, what is the headless browser main feature? All these actions are performed, but they just occur in the background and are carried out through API calls and commands.

Running processes with a true browser involves:

1. Initialising and using a library like Node.js or specific API such as Chrome DevTools Protocol or WebDriver.
2. Sending HTTP requests to get a specific webpage’s HTML code.
3. Processing its JavaScript, HTML and CSS.
4. Interacting with components of the page (clicking, filling forms, etc).
5. Processing and extracting data
6. Output the processed data, in console or saving to a CSV file.
7. Finalizing the operations.

Important: The lack of output viewing does not inhibit the browser from functioning. This feature makes headless browsers preferable for testing, web scraping, CI/CD, and automation, where the visual result of actions taken is not important.

Difference Between a Regular and a Headless Browser

If making a comparison, the differences go far beyond mere differences in the interface. The latter has an entirely different method of interacting with the particular website. Hence, let us understand the other distinguishing characteristics in the table below.

From this comparison, we understand that a development environment is required, and proficiency in console interaction and programming languages is essential for the first type to operate.

Analyzing the differences, we can presume that these tools will have different application areas which leads us to ask: what is a headless browser used for and in which instances?

Examples of Headless Web Browser Usage

These are the fields where such technology are most frequently applied:

• Development;
• Testing;
• Automation of actions;
• Web scraping;
• Continuous integration;
• Network monitoring;
• Rendering;
• Security auditing.

The scope of a headless tool is not limited to the above-mentioned tasks. It also encompasses actions associated with diagnosing problems, managing and protecting traffic, detecting suspicious activities, and reporting activities that are necessary for compliance analysis required by regulations.

Headless Browser Applications in Development

Integrating services and developing web applications are two of the many tasks such tools assist services with.

This tool is most effective in the following scenarios:

• Modular or unit testing. It gives opportunities for verification of single code modules for correctness. Developers create automatic user interface testing where each interface component such as forms, input boxes, buttons, lists among others is tested in isolation for functionality.
• Combined with CI/CD. Integration of these tools with continuous integration systems like Jenkins, Git lab CI greatly facilitates early code error detection and consequently, rectification before release.
• JavaScript code troubleshooting. Used for diagnosing and scripting interface or JavaScript code errors.
• Cyber security: Helps in finding security weaknesses and improving defense levels.

Such tools in development are not limited to the above mentioned scenarios. As technology evolves, programmers are challenged to develop new, flexible solutions to automate interaction with web resources.

What is Headless Browser Testing Main Features

QA and AQA specialists put their trust in such tools more than any other because they are very light and fast. Hence, these offer advanced testing capabilities for web pages and applications.

The primary application scenarios in this area comprise:

• Multi-platform cross headless browser testing;
• Verification of elements within the user interface;
• DOM Manipulation;
• Network communication handling;
• Website design auditing;
• Time saving when re-initializing parallel tests;
• Evaluation of JavaScript execution for graphic representation;
• Session capturing for later replay;
• Remote or virtual machine testing;
• API test cases.

It is evident that the tool enables testers to carry out tests with a high degree of flexibility and swiftness which in turn impacts test accuracy and the resulting product is likely to be of better quality.

Headless Browser Scraping for Data Collection

Marketers and SEO experts can scrape sites for relevant data using headless mode for effective product marketing. However, they often run into blocks, which leads to a lack of resources. But why does this happen?

Consider two requests below.

Banning systems that IP addresses for all sorts of infractions need to ascertain whether the request is coming from a bot or natural user for a certain header in the ordering list. A user request from Google Chrome is displayed on the left, while a request coming from a headless browser is on the right.

How do you parse data if there is a chance you might get banned? The integration of proxy for headless browsers that mask their real IP address through correct HTTP request formulation is possible. Hence, one is better off starting with a using a proxy for data parsing so information can be pulled selectively with the use of CSS or XPath, elements can be clicked on, and the data can be placed in the required files easily.

Best Headless Browser for Scraping

Performance, technologies used, design, as well as functionality often determines the tools of choice. One can get multiple tools that offer different techs and UI. Their Foundation, Engine, and API are what distinguishes them.

Every tool claims to be the best, yet that is too subjective. In reality each tool employs different logic and technology in dealing with web content certain methods. Nevertheless, they can be conveniently split into two categories: browsers and “headless” libraries.

First category include:

• Chrome: engine – Chromium; API: Chrome DevTools protocol;
• Firefox: engine – Gecko; API: WebDriver.

Puppeteer, Playwright, Selenium, and PhantomJS allow for remote control.

Let’s focus on these three most popular ones since the last one is more rarely used.

The selection of the best tools from the above is based on the projects you are engaged with as well as the resources utilized.

For action automation, testing, and data extraction, users prefer Chrome and Mozilla Firefox due to their unrivaled performance and modern technology support.

If you are developing a project on Windows OS, know a programming language, and need speed, then consider using Puppeteer.

If you are developing web applications on macOS, then Playwright will do a better job in accomplishing the given assignments.

For browsing, testing, and action automation, one can use Selenium.

What is a Headless Browser Preferable Use Cases?

They are outstanding when working with automation and performance tasks and, in general, have a myriad of other benefits, including:

• Optimal speed and faster startup;
• Lower CPU and RAM consumption;
• Enhanced multitasking and scalability;
• Ability to automate mundane tasks;
• Cross-platform use;
• Integration of third-party solutions.

These applications are ideally suited for use in backend and service solutions, as well as in resource constrained environments.

When is Headless a Bad Idea?

Before implementing any tool, it is worth understanding the intricacies of such browsers:

• Not applicable to visual and design analysis;
• Requires some level of programming and console interaction;
• Limited ability to engage with elements of the interface;
• Can be flagged as a bot quite easily;
• Not user friendly when it comes to debugging.

What is a Headless Browser: Final Thoughts

We now have an understanding of what headless browsers are – these are new age technologies in the development, testing, and scraping realms. Their most noteworthy benefit is the conservation of resources, as these do not need a graphical user interface to be executed.

For software developers and testers, these have become instrumental in the construction of robust, repeatable, and rapid CI/CD pipelines, as these allow for quick testing under numerous conditions which is critical for cross browser compatibility.

In the case of SEO, these tools become critical when analyzing a website, checking its indexation, or executing multiple actions on the document like simulating page usage or collecting data for analysis.