Working with a 4k laptop has been quite nice. There are many scaling features that account for various desktops (mine is currently Unity on Ubuntu 14.04). The text within Firefox does scale within itself. While it may be cumbersome to change the setting in a separate places, there certainly are some benefits.
With the difference in scaling, you can set the web browser scaling slightly larger than the rest of your desktop. Lets face it, clicking an icon is easy, even when it is smaller. Reading a webpage with perceived an serif 4 font? Instant headache.
As for the settings, within Firefox, you want to browse to the handy about:config page and search for the string “layout.css.devPixelsperPx”. This setting allocates the scaling of the application. To make Firefox twice as large, input 2. To make Firefox half as large, input .5. As you begin to drop below 1, some of the default icons within Firefox’s title bar become cut off.
For my laptop’s 4k display, I currently run the Ubuntu 14.04 OS at x1.5 scaling. It does make the display slightly small, but it feels nice and clean. The same scaling is not quite as nice within a web browser and as such, the current setting in Firefox is 2.
This then changes when I sit down in my home office. With two external 32″ displays only at 1920×1080, the scaling needs modified. I slide my desktop over to x.875 and my Firefox to 1.
For now, its only a few clicks. Maybe a script some day to automate my home office versus laptop screen, but that can be saved for another post.