Qt 5 Support Is Ending – What You Need to Know

Standard support ends May 26, 2025. Here’s what it means for your team—and how to start planning.

TL;DR

After May 26, 2025, there will be no community updates or security patches for Qt 5 [1]. Continuing to rely on unsupported versions means knowingly exposing users to vulnerabilities. In some regions, such as the EU, new legislation places liability directly on vendors who fail to maintain secure software.

  • Updates, bug fixes, and security patches will require a Qt commercial license.
  • Licensing costs will increase significantly (at least 2× commercial Qt license).

If your applications are built on Qt 5 and you’re not yet on Qt 6, now is the time to start planning. We’re offering a free, no-commitment technical advisory workshop to help teams affected by Qt 5 End-of-Support and provide a migration path to Slint, a modern UI toolkit built by former Qt engineers. We helped SK Signet migrate their Qt 5 codebase to Slint and standard C++ in about four months [2].

📩 Contact us to schedule your migration readiness session.

🤔 Is Sticking with Qt 5 a Viable Strategy?

After May 26, 2025, the Qt Company will no longer provide community updates or security patches for Qt 5, unless under a costly Extended Security support, which is atleast 2x the commercial license:

Each software developer will additionally need an active Qt Developer License. The subscription does not include Technical Support, assistance applying the patches, or patches for 3rd party libraries or dependencies. Support is specific to a Qt software version and includes a max. 5 hours of work per ticket, additional hours available as service [1].


Since the beginning of 2025, the Qt framework has seen three critical security fixes—two of which affected Qt 5 versions [3]. This highlights the ongoing importance of security maintenance for any software stack built on Qt. Continuing to rely on unsupported versions means knowingly exposing users to vulnerabilities. This is not just a technical risk, but increasingly a legal one. In the European Union, for example, the Cyber Resilience Act (CRA) [4] requires software vendors to take responsibility for known security issues, placing legal liability directly on providers who fail to maintain secure software.

Qt 6 is Not a Drop-in Replacement

🧩 API and Module Changes

While Qt 6 retains much of the Qt 5 API, several modules have been removed, restructured, or rewritten:

  • Qt Script has been removed in Qt 6. Teams relying on it will need to refactor their logic.
  • Qt XmlPatterns was removed, impacting projects using XQuery or XPath processing.
  • Changes to QVector/QList semantics may require adjustments in code.
  • The Qt OpenGL module has been replaced with a lower-level rendering stack using Rendering Hardware Interface (RHI), which could break custom OpenGL-based rendering logic.

⚙️ Behavioural Differences

In addition to API changes, subtle behavioural differences may impact your project:

  • Text rendering and layout behaviour differs due to the adoption of HarfBuzz in Qt 6.
  • High-DPI scaling now uses a different model by default, which affects how your UI appears on 4K/Retina displays.
  • QML type system was overhauled for better integration with CMake and static analysis, but this breaks some older import patterns and dynamically registered types.

💸 Budget impact

Migrating to Qt 6 requires planning, quality assurance, resource allocation, and time.

If you're on a commercial license and are unable to move to Qt 6, you’ll need to purchase an Extended Support [1] license in addition to your Qt commercial license. Extended Support is limited to five hours per support ticket and applies only to specific Qt versions.

Additionally, commercial Qt licensing costs have been increasing [5], so even if you manage to migrate to Qt 6, the cost of maintaining your codebase on Qt is expected to rise over the coming years.

For open-source users, no further updates or patches will be available after the end of standard support. Continuing to use an unsupported version of Qt can introduce significant risks, including technical debt, security vulnerabilities, and blocked upgrades—particularly for embedded, industrial, or long-lifecycle applications.

🔍 Strategic decisions

If you’re reviewing your stack in light of this change, now might be a good time to:

  • Evaluate open-source or more modern alternatives.
  • Reduce vendor lock-in.
  • Optimize for runtime performance and binary size.
  • Future-proof your development by adopting tools with active community and commercial backing.

🚀 Why Consider Slint as an Alternative?

Slint is a modern UI toolkit built by former Qt engineers—designed specifically to address many of the pain points developers face with legacy stacks [6]. Here’s why it’s gaining traction:

  • ✅ Modern Architecture – Built for modern workflows with strong support for embedded, desktop, and cross-platform development.
  • ✅ Language Flexibility – Keep your application logic in C++, or you can also use Rust, JavaScript, or Python, allowing you to pick the best language for your use case.
  • ✅ Performance First – Slint scales from devices with GPU support down to micro-controllers with just a few hundred kB of RAM.
  • ✅ Design Tooling - Slint supports a modern UI workflow with Figma plugin support, real-time previews, and editable sample data—making it easier to iterate and validate your designs.
  • ✅ Affordable Licensing – Slint’s licensing is simple and cost-effective, with a transparent pricing model [7].
  • ✅ Proven in Production – Companies like SK Signet, OTIV, Stromer have already made the leap [8].

🎯 Free Technical Workshop (No Cost, No Commitments)

We’re offering a free, no-commitment technical advisory workshop to help teams affected by Qt 5 End-of-Support. We helped SK Signet migrate their Qt 5 codebase to Slint and standard C++ in about four months [2]. The workshop will help you:

  • Map dependencies and explore open-source alternatives.
  • Develop a migration plan to Slint that includes effort estimates.
  • Gain clarity on the next steps to ensure a smooth transition.

📩 Contact us to schedule your migration readiness session.

Final Thoughts

Whether you plan to continue with Qt 5 via commercial licensing or explore alternatives, it’s crucial to start the conversation early. We’ll collaborate with your team to estimate the effort and complexity of migrating to Slint—removing the guesswork.

References

  1. https://www.qt.io/blog/extended-security-maintenance-for-qt-5.15-begins-may-2025
  2. https://slint.dev/success/sksignet-evcharger
  3. https://www.qt.io/blog/tag/security
  4. https://digital-strategy.ec.europa.eu/en/policies/cyber-resilience-act
  5. https://www.reddit.com/r/QtFramework/comments/1hhq4if/comment/m2wus4r/
  6. https://slint.dev/alternative-to-qt.html
  7. https://slint.dev/pricing/
  8. https://slint.dev/showcase/
  9. https://www.reddit.com/r/QtFramework/comments/170ffak/is_qt6_a_good_move/
  10. https://geant4-forum.web.cern.ch/t/g4-11-2-2-qt6-problems-on-windows/12530/4

Slint is a Rust-based toolkit for creating reactive and fluent user interfaces across a range of targets, from embedded devices with limited resources to powerful mobile devices and desktop machines. Supporting Android, Windows, Mac, Linux, and bare-metal systems, Slint features an easy-to-learn domain-specific language (DSL) that compiles into native code, optimizing for the target device's capabilities. It facilitates collaboration between designers and developers on shared projects and supports business logic development in Rust, C++, JavaScript, or Python.