I wrote this tutorial from the perspective of Windows users since headless mode just arrived there today, but the steps should be pretty similar from Linux or macOS when headless functionality arrives there.
This is great news that FF Headless has finally hit Windows! The QA lead at my company uses Selenium for a lot of our front-end testing and I’m very curious to get more involved with it.
Huh. I didn’t know headless mode worked anywhere? The impression I got was that headless mode in Firefox was one of those features that kept getting attempted on branches and then dropped again a couple years later each time the person trying to land it gave up.
At $oldjob we used to run Firefox connected to Xvnc. No physical display needed, you can start as many of them simultaneously as you’d like to and, helpfully, if anything REALLY mysterious happens, you can even use vncviewer to connect to it and look at what the Firefox instance thinks it’s doing.