SumatraPDF dark mode

SumatraPDF is a lightweight PDF reader (here). To give you an idea, its installer is less than 10 MB (around 5 MB for version 3.1.2, which I still use due to a bug in 3.2, and 9 MB for version 3.2), where Adobe Acrobat Reader’s installer is over 150 MB.

I wanted to read some books in it, but the (usual) white background is a bit hard on the eyes. SumatraPDF doesn’t provide a dark mode as-is, however it provides a way to customize a lot of things in its UI… including background and font colors. Long story short, you can make your own dark mode. Quite easily, if you have some very basic knowledge of HTML colors codes: go to Sumatra’s menu, then Settings -> Advanced Options. This will open a text file, SumatraPDF-settings.txt, containing a bunch of settings (possibly all?), and even your recent file history, if you chose to keep it.

In this file, go to the FixedPageUI section (which should be quite close to the top of the list). Then edit TextColor and BackgroundColor at will. I chose #cccccc for text and #333333 for background. Note that 3-letter short color codes (like #ccc) won’t work here (yes, I tried, I’m that lazy ^^). In Sumatra 3.2, you also have GradientColors, which is the color of the windows background outside of the page, but in Sumatra 3.1.2 that setting is absent (and I tried adding it and it didn’t work).

The settings should apply as soon as you save the file. If not, I guess you can always restart Sumatra.

Note that this does have an annoying side effect: if the PDF you read contains pictures with a transparent background, they’ll probably look very weird. I don’t think there’s a fix for this, so I just skip the pictures, or if I really must, I put the text and background color back to respectively black and white.

Update (2021-05-03): “pale” mode

As I mentioned above, this dark mode is often problematic when viewing pictures. I also had, on occasion, text that would remain black, over my black background, making it impossible to read.
So I eventually gave a shot to another configuration, using this time some kind of dark-ish grey for text and some not-as-dark grey for background. This results in a pale but globally eye-relaxing (IMO) theme, although I noticed its lack of contrast forces me to zoom a bit bigger to be able to read comfortably. The big plus is I haven’t encountered any text or picture that was rendered totally unreadable by this setup. My values are:
TextColor = #333333
BackgroundColor = #bbbbbb