Am I allowed to create a closed-source application using the LGPL licensing scheme for Qt if I use Qt Designer to generate its user interface?

I originally thought this was possible until I saw this section in their licensing comparison chart:

Tools open source licensing

Now I still have some doubts, maybe this only applies to the Designer tool itself (in case I wanted to distribute it with my application) or just to the generated UI (xml files if I remember correctly)?

  • 1
    The relevant GPL FAQ item is gnu.org/licenses/gpl-faq.en.html#GPLOutput, but I am not sure whether the second paragraph applies to Qt's UI builder output or not. (Someone who understands the tool's operation better could certainly answer this, though.)
    – apsillers
    Dec 13, 2018 at 0:13
  • @apsillers AFAIK, Designer allows me to visually create the UI from some GUI elements (buttons etc). The output is an XML file which then can either be read/interpreted by my application to create its GUI during runtime or compiled into application source code which will be compiled into the executable. I don't think the section of the GPL you linked to prevents me from doing either as Designer's output is (at least in some sense) generated by me (operating it), but I'm not a lawyer.
    – FriendFX
    Dec 13, 2018 at 0:27
  • The open source Qt Creator IDE and the Designer are GPL, not LGPL. Do you want to distribute either of those things along with your application? (I guess not).
    – Brandin
    Dec 13, 2018 at 6:00
  • 2
    By the way, that comparison chart should be treated as a sales tool, not a good source of information. For specific questions, the FAQ is probably more accurate: Qt Legal FAQ
    – Brandin
    Dec 13, 2018 at 6:04

1 Answer 1


Yes you are allowed to do so. Qt Designer is available under not just GPL but "GPLv3 with The Qt Company GPL Exception 1.0"

Here is the exception:

The Qt Company GPL Exception 1.0

Exception 1:

As a special exception you may create a larger work which contains the output of this application and distribute that work under terms of your choice, so long as the work is not otherwise derived from or based on this application and so long as the work does not in itself generate output that contains the output from this application in its original or modified form.

Exception 2:

As a special exception, you have permission to combine this application with Plugins licensed under the terms of your choice, to produce an executable, and to copy and distribute the resulting executable under the terms of your choice. However, the executable must be accompanied by a prominent notice offering all users of the executable the entire source code to this application, excluding the source code of the independent modules, but including any changes you have made to this application, under the terms of this license.

Exception no.1 fully covers your question.

Here's the repository for Qt tools https://github.com/qt/qttools. There you can find the source code for Qt tools (including Qt Designer) and its licenses.

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