Usually it is recommended to either use GTK or Qt apps in the operating system, but not mixing them both together.


When using KDE it seems to be obvious to use KMail (Qt) instead of Thunderbird (GTK).

Or: When using Gnome it is recommended to use Thunderbird instead of KMail.

My question is: Are there any disadvantages in relation to CPU efficiency/task handling speed when mixing up both application types?

  • 2
    No, it absolutely doesn't matter. You can run multiple Gtk or Qt apps even on older machines, but KDE or Gnome monsters + their respective ecosystems are each capable to bring a machine to its knees on their own ;-)
    – mosvy
    Sep 5 '19 at 21:10
  • i agree that GTK vs QT doesn't matter. It will be Gnome or KDE that brings the system to a crawl.
    – ron
    Sep 6 '19 at 1:24
  • 1
    Related on Ask Ubuntu: Is it bad to have Qt apps on a GTK environment?, which was asked and then closed in 2016--I wrote a long answer over there to demystify the issue; no benchmark to prove though.
    – user125388
    Sep 6 '19 at 9:28

It will use more RAM and cache, because of the extra libraries. This will cause a slow down (more swapping, if RAM is low; more cache misses). However you will probably not notice.

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