ubuntu 17.10 & Firefox DPI Scaling

Question

I'm using Ubuntu 17.10 on a Dell XPS 13 with a 3200x1800 screen and while most native applications seem to scale okay using the "Scale" option in my display settings, Firefox seems to render at a lower resolution and "scale up", causing all graphics and especially fonts to be blurry. Is there something I can do to fix this? It's nice that many/most programs behave, but frustrating that the programs I use 95% of the time (FF & Atom) scale so poorly.

Here's an example demonstrating the issue. FF and the settings app:

Solution

Firefox has its own DPI mode, not always plays well in a desktop environment with modified DPI, yet the solution is simple:

First go to a firefox tab and type: "about:config", next in the search bar type: "layout.css.devPixelsPerPx" now change the Value to what you like.

If the decorations or the text is blurry, you may want to use a decimal value to make firefox more aesthetic, go for ".7". Or to make it bigger to a 2 or 1.5.

My screen is 15 inches 1080p; a value of 1.3 worked fine for me. The info came from this page:

https://fedoramagazine.org/how-to-get-firefox-looking-right-on-a-high-dpi-display-and-fedora/

Comments

[Videonauth]

Welcome to Ask Ubuntu! A link to a potential solution is always welcome, but please add context around the link so your fellow users will have some idea what it is and why it's there. Always quote the most relevant part of an important link, in case the target site is unreachable or goes permanently offline. Take into account that being barely more than a link to an external site is a possible reason as to Why and how are some answers deleted?.

[Plaid Phantom]

that would help me change the size of Firefox elements, but that is not what I need. Firefox (or maybe it's gnome) respects the scaling I want, but it seems to render onto a smaller canvas and "scale up", even if I change devPixelsPerPx to .66 to reverse my current 150% scaling. Honestly, if Firefox would just ignore the OS scaling as it does in the linked article I wouldn't have any problem.

[Eduardo Montero]

try change devPixelsPerPx to 1.0 or -1.0