What is a Headless Browser?

A headless browser is a web browser without graphic elements, a so-called Graphical User Interface (GUI). Headless browsers are run via command line or network communication.

Running without the GUI means that a headless browser can still function as a regular browser and perform various tasks, such as uploading documents, presenting data, and contacting target websites. The main difference is that headless browsing happens at the backend and doesn’t involve any graphic display, such as pictures, icons, or similar visual elements.

Headless browsers are mainly used for automated tests, data extraction, and various headless testing tasks. The main benefit of a headless browser is its ability to run quickly and without interfering with the front end of the target website. However, headless browsers also have some limitations that you’ll learn about in this article.

What is a Headless Browser Used for?

A headless browser has multiple use cases. We listed and explained the main ones:

Data Collection

Headless browsers are often used for data collection because they can help extract specific data points from the target site. They make web scraping more efficient since headless browsers don’t need to load graphic elements.

With a headless browser, you don’t need to write request chains one by one, and you can run JavaScript.

Layout Testing

A headless browser can help test website layout to ensure the front-end of a website looks as planned. Developers and designers use headless browsers to automate layout screenshots, test specific element color selections, AJAX execution, and perform various layout checks.

Automation Testing

Developers use headless browsers to automate software maintenance and perform quality assurance tasks. For example, headless browser automation allows checking if submission forms on web apps work as intended.

Performance Monitoring

Headless browsers can help monitor website performance. Websites without the GUI load much faster and allow tasks without the user interface interaction to be tested via the command line. Pages don’t have to be refreshed manually, which saves time and effort.

What are the Advantages and Disadvantages of a Headless Browser?

When it comes to the pros of headless browsers, here are the main advantages:

• Speed. Headless browsers are much quicker than regular browsers. They can load JavaScript and CSS faster because they don’t need to open and render HTML elements.
• Efficiency. This is especially relevant for data extraction. Headless browsers can help collect specific data points from the target websites, for example, pricing data on an e-commerce website.
• Simplicity. Developers can save time by using headless browsers because they allow utilizing command lines. For example, this can be applied when testing code changes.

However, headless browsers also have a few drawbacks:

Fast loading can make it harder to notice and debug various issues.
Headless browsing only reveals backend issues, which means that it may not catch potential issues at the front-end of a website.

What are the Most Popular Headless Browsers?

A headless browser can be used for task automation.png

Developers often test various headless browsers for different tasks because some of them perform better than others in specific testing cases. Trying out different browsers allows developers to find the right combination of tools for their tasks.

Here are the most popular web browsers for headless use and their primary features:

• Mozilla Firefox is a well-known web browser which has a headless mode. The headless Firefox is often used with the Selenium framework. This browser can be efficiently used for headless testing.
• Google Chrome runs in a headless environment if it’s in version 59 or any version released after it. In headless mode, this browser can help create PDFs, get screen captures, or print the Document Object Model (DOM).
• HtmlUnit is supported by JavaScript libraries. This headless browser can be used for website automation since it can reduce manual efforts for various user interactions with a website. For example, it can automatically test submission forms and website redirects.

What is Headless Browser Testing?

Headless browsers are mainly used for web page testing. The reason for that is a headless browser’s ability to understand HTML content and interpret it as any regular web browser would. Headless browsers can perform tests without the usual GUI, which allows the software to test various website components while skipping visual element rendering.

Testing in a headless environment enables users to run tests faster than with a regular browser. However, headless browser testing has a few limitations that are worth mentioning.

What are the Limitations of Headless Browser Testing?

Headless browsing for website testing comes with a few risks:

Headless browsers highlight the bugs that appear in a headless mode. This means that regular users will rarely run into these issues since they surf the web in a typical browser environment. It’s important to remember this limitation because some developers end up solving issues that are often irrelevant to regular users.
Headless testing helps websites load quickly, which is often an advantage. However, fast loading can make locating elements with inconsistent failures difficult.

These limitations can be solved by being careful and staying aware of the potential issues. Many users choose to utilize different browsers, which can help spot various bugs better.

Conclusion

Now that you've learnt what is a headless browser, you can imagine how it may help make developers’ lives easier. These browsers run in the backend without interfering with the front-end of a website and can quickly test various website features, such as redirects, submission forms, etc.

The main headless browser use cases include data extraction, automation, headless testing, and performance monitoring. There are various types of headless browsers, including the most popular regular browsers in a headless mode, such as Mozilla Firefox and Google Chrome.

While these browsers have a number of benefits, they also have a few limitations that users should be aware of. For example, it’s essential to keep in mind that a headless browser only interacts with the backend of a website. Hence, it only flags bugs that are relevant to the backend and do not necessarily interfere with the user experience.