Not a headless browser by itself, it does allow to run almost any X application (including common browser) on a headless server though. You can then control the browser via WebDriver.
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Pro You can launch REAL browser using xvfb
Just test in real-world browser - xvfb makes it possible to launch them without the real screen.
Con Problem with ports
If you are running multiple instances on some browser and you use xvfb to run instances on agents on Bamboo or Jenkins you will potentially have a problem with using ports.
The first instance you are starting takes on a port on the agent and then the second instance that would be run doesn't have a port to go to.
You can partially solve the problem by dynamically assigning the next available port to the new instance that comes to be executed.
This only works if we assume that all the instances start in different time intervals, but what you cannot know is which instance is going to get a port first if they start at the same time, then the instances will crash, those that started at the same time.