Licensing Differences Between PyQt6 and PySide6

If you're getting started with Python GUI development, you've probably noticed there are two main bindings for the Qt framework: PyQt6 and PySide6. The APIs are almost identical, so a natural question comes up — when should you use PyQt6 and when is PySide6 the better choice?

This is a great question, and understanding the answer will help you make a confident choice for your own projects.

The Licenses at a Glance

PyQt6 is available under the GNU GPL v3 license, or under a commercial license from Riverbank Computing (the developers of PyQt6). If you want to use PyQt6 without following the terms of the GPL, you need to purchase a commercial license.

PySide6 is available under the LGPL v3 license. The LGPL is more permissive than the GPL, which gives you more flexibility when distributing proprietary or closed-source software.

Both the GPL and the LGPL are open source licenses, but they come with different obligations — and that difference matters depending on what you're building.

What Does the GPL Require?

The GPL (GNU General Public License) is a copyleft license. If you distribute software that uses a GPL-licensed library, your entire application must also be released under the GPL. In practice, this means:

• You must make your source code available to anyone who receives your software.
• You cannot distribute your application under a proprietary or closed-source license.

For open source projects, academic research software, or internal tools that you don't distribute, this is perfectly fine. The GPL only applies when you distribute the software to others.

What Does the LGPL Require?

The LGPL (Lesser General Public License) is less restrictive. You can use an LGPL-licensed library in a proprietary application, as long as you:

• Dynamically link to the LGPL library (rather than statically bundling it into your binary). In practice, Python applications naturally do this because they import PySide6 as a separate package.
• Provide a way for users to replace or modify the LGPL-licensed component. Since PySide6 is installed as a standard Python package, users can update or replace it themselves.
• Include a copy of the LGPL license with your distribution and make it clear which parts of your application are covered by it.
• Provide access to the LGPL source code (for PySide6 itself, not your own application code).

You do not need to open-source your own application code.

Why is PyQt6 Still the Most Popular Choice?

Given the licensing difference, it might seem like PySide6 is the obvious choice. But there are several reasons why PyQt6 has remained popular:

PyQt6 came first

PyQt6 had its initial release in 2016, while PySide6 didn't arrive until 2018 — and its early releases had quite a few bugs. By the time PySide6 matured, PyQt6 already had a large user base, extensive community support, and widespread adoption. That momentum built up over years, and many tutorials, Stack Overflow answers, and third-party tools were written with PyQt6 in mind.

The GPL isn't always a problem

For many use cases, the GPL's requirements are a non-issue. If you're building open source software, academic tools, or internal applications that never get distributed, the GPL places no meaningful restrictions on you. Open source licenses are standard in research and scientific computing, for example.

Commercial licenses offer support

Some companies may prefer paying for a commercial PyQt6 license. In exchange, they get direct support from Riverbank Computing and the freedom to use their own proprietary license. For businesses, a paid license with support can be more attractive than a free-but-unsupported option.

Minor API differences

While PyQt6 and PySide6 are very similar, there are small differences in how they handle certain things. For instance, PyQt6 has a slightly different (and some would say more convenient) approach to loading .ui files created in Qt Designer. These differences are minor, but developers who are already comfortable with one framework tend to stick with it.

Which Should You Choose?

For most new projects, the practical differences between PyQt6 and PySide6 are small. Here's a simple way to think about it:

Consideration	PyQt6	PySide6
License	GPL v3 (or commercial)	LGPL v3
Open source projects	Yes	Yes
Closed-source / commercial	Requires paid license	Free under LGPL terms
Community & resources	Large, established	Growing, well-supported
Backed by	Riverbank Computing	The Qt Company

If you're building something open source, either one works well. If you're planning to distribute closed-source commercial software and don't want to pay for a license, PySide6 gives you that flexibility under the LGPL. If you want commercial support, PyQt6 may be the better choice.

The good news is that switching between them is straightforward. The APIs are nearly identical, and most code can be converted from one to the other with only minor changes. For a detailed comparison, take a look at our guide on the differences between PyQt6 and PySide6.

The best approach? Try both, and convert a small project from one to the other. You'll quickly see how similar they are — and you'll feel confident that whichever you choose, you're not locked in.