# Thunderbird UI font size on HighDPI

I cannot figure out how to increase the menu font size or the message list font size in Thunderbird. I've tried:

1. Increasing the font sizes in Thunderbird preferences (no effect on anything)
2. Setting a minimum font size of 20 in Thunderbird preferences (no effect on anything)
3. Setting the layout.css.devPixelsPerPx in about:config to 2 (only affects mail bodies, and not much else)
4. Setting the X font DPI in .Xresources (no effect on anything)
5. Setting the font size in the KDE systems settings pane for GTK (no effect on anything)
6. Setting the font size in lxappearance (only affects lxappearance itself, not Thunderbird - and lxappearance itself resets back to normal after restarting it!)

I am using KDE on Fedora 23 and I already have KDE configured for HighDPI (although much of KDE is still broken because it uses fixed pixel sizes).

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answered 2016-01-09 07:42:30 -0500

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Because I am using KDE, I needed to set the display scaling to 1.5 or 2 in KDE system settings, and I needed to make sure that "force font DPI" in fonts was unchecked - also in system settings.

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Try installing gnome-tweak-tool and changing "scale" in the Font section. That should change font size in all GTK2 and GTK3 apps. If your resolution is big enough, you can go to the Windows section and set scaling to 2 there. It will scale all GTK apps (not sure if it works for GTK2 apps though).

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