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:

enter image description here


Firefox has its own DPI mode, not always plays well in a desktop environment whit 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:


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  • 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. – Plaid Phantom Nov 4 '17 at 5:22
  • try change devPixelsPerPx to 1.0 or -1.0 – Eduardo Montero Nov 4 '17 at 21:10

I was happy to scale the browser UI chrome as well as the page content, so layout.css.devPixelsPerPx worked for me.

But if you want to change the default zoom of the page content only, without affecting the UI at all, I recommend the Zoom Page WE extension.

You will probably want to open Menu > Addons > Zoom Page WE > Zoom Levels & Font Size and set Default Full Level to your desired zoom, e.g. 120%.

This will set the default zoom for newly opened websites, but if you adjust the page zoom then that value will be remembered for the current site in future. (Unless of course you have set browser.zoom.siteSpecific: false)

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