Coincidence or not since version 57 Firefox supports a headless mode. Chromium also introduced this feature at version 57.
firefox --headless --screenshot shot.png https://dev.webonomic.nl
Will run without GUI and put a screenshot in your working directory called shot.png. If you omit to specify the a filename, the default is screenshot.png.
Since Firefox stable is now at version 56, you’ll need Firefox-developer for now to get this working.
Another nice thing is the format of the screenshot that is created. For width it will take the device-width, the resolution of your desktop, but it will render a full website, 100% height, sot it will output the layout-viewport, not just the visual viewport.
To get the visual-output you need to set the window size option:
firefox-developer --headless --window-size 360,640 --screenshot https://dev.webonomic.nl
This will create a responsive layout (mobile phone Galaxy S5 dimensions) for this website.
For the moment only the png format seems to be supported. If you try saving to a screenshot.jpg file you’ll end up with a png file called screenshot.jpg
User-agent Firefox –headless
Mozilla/5.0 (X11; Linux x86_64; rv:57.0) Gecko/20100101 Firefox/57.0
this is actually the same User-Agent as manually running Firefox as a browser. I take that as a plus; if we want the Internet of Things (IoT), it should be a democratic Internet of Things.
Tags: firefox