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A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11To migrate an existing Qt 6 application to Qt 6.12 LTS, first compare the 6.12 change notes with the Qt modules and APIs your project actually uses. Then install a Qt 6.12 kit that matches your compiler and target platforms, reconfigure and build from a clean build directory, fix any relevant compatibility issues, and test the deployed application on its real targets. This is a Qt 6 minor-version upgrade—not a repeat of the general Qt 5-to-Qt 6 port.
Qt announced Qt 6.12 LTS on September 30, 2026, and says it receives maintenance over a five-year period. That is Qt’s stated maintenance horizon; it does not by itself establish a particular commercial support entitlement for your product.
1. Inventory your current Qt 6 project
Before changing kits or build files, record the configuration you have today. This makes it easier to distinguish a Qt 6.12 issue from an existing build or deployment problem.
- Current Qt 6 version and the Qt modules linked by the application.
- Compiler, compiler version, and CPU architecture for each build.
- Build system and configuration, including CMake or qmake, presets, toolchain files, and custom scripts.
- Generated code, plugins, third-party libraries, and any Qt compatibility code.
- Every operating system and architecture you ship to, including the versions your product promises to support.
Use this inventory as the filter for the rest of the migration: the relevant changes are those that intersect your APIs, modules, build configuration, and shipped targets.
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2. Check the Qt 6.12 changes that affect your code
Read the Qt 6.12 changes module by module. Look for API changes, deprecations, behavior changes, and platform-specific notes that match your inventory. Do not assume every listed change affects your application, and do not treat historical Qt 5 removals as newly introduced Qt 6.12 breaks.
Example: QMediaMetaData thumbnail
Qt’s 6.12 notes deprecate QMediaMetaData::ThumbnailImage and say backends will no longer populate it. If your media code relies on that value, update it to use CoverArtImage and test the behavior with the media backends and files your application supports.
3. Confirm that Qt 6.12 supports each destination configuration
Check the Qt 6.12 supported platforms information for every operating system, CPU architecture, compiler, and module combination you ship. Qt says configurations not listed are not officially supported, and configurations may change in later 6.12 patch releases. A compiler or operating system supported by your previous Qt 6 version is not automatically supported by 6.12.
Plan separately for Windows 10
Qt 6.12 supports Windows 10 version 1809 or later, and Qt identifies 6.12 as the last Qt version to support Windows 10. If your product targets Windows 10, decide how that target will be handled beyond Qt 6.12 rather than assuming a later Qt release will retain support.
4. Install a matching Qt 6.12 kit and reconfigure cleanly
Install the Qt 6.12 components you need along with a compatible compiler and toolchain. A working Qt 6.12 installation alone is not enough: the selected kit must fit the operating system, architecture, and compiler configuration for the target.
For CMake projects, use Qt’s CMake getting-started guide to check the expected package and target pattern. A minimal example is:
find_package(Qt6 REQUIRED COMPONENTS Core)
target_link_libraries(my_app PRIVATE Qt6::Core)Qt’s guide also describes qt_standard_project_setup() for standard project defaults, including automatic MOC setup, and qt_add_executable() for creating an executable target. Treat those as documented patterns, not a requirement to replace a functioning project structure during a version upgrade. Qt 6 requires a compiler that supports C++17 or later; the supported-platform information determines which specific compiler and platform combinations are supported.
- Switch the IDE or build configuration to the Qt 6.12 kit and its compatible compiler.
- Remove or isolate the old build directory so cached package paths and generated files do not keep pointing at the previous Qt installation.
- Run a fresh configure step using the project’s normal CMake or qmake workflow.
- Confirm the configure output resolves the intended Qt 6.12 installation, modules, compiler, and target architecture before building.
5. Build and address project-specific issues
Build with the same configurations you use for release, and start with diagnostics tied to code or modules your application actually uses. If a warning or error concerns an API mentioned in the 6.12 change notes, follow that entry and update the affected code. Keep unrelated cleanup separate where practical so that regressions are easier to trace.
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For CMake, confirm that required components are found and that targets link against the intended imported Qt targets, such as Qt6::Core. For either build system, check custom plugins, generated code, and packaging scripts as well as the main executable; a successful compile does not establish that deployment is complete.
6. Validate the application on its shipped targets
Run the project’s existing unit, integration, UI, packaging, and deployment checks for each supported target configuration. Test the installed or packaged application, not only a developer build.
- Exercise the features that use Qt modules or APIs affected by 6.12 changes.
- Check startup, plugin loading, multimedia behavior, and other module-specific workflows used by the product.
- For Qt Quick or other graphics-heavy interfaces, verify rendering and interaction on the actual target hardware and operating systems. The Qt 5-to-Qt 6 transition involved a graphical backend change; that history is a reason to test graphics carefully, not evidence that the same change recurs in this Qt 6.12 upgrade.
- Verify packaging and runtime deployment for every OS and architecture in your release matrix.
7. Decide whether Qt 6.12 LTS fits your maintenance needs
Qt describes 6.12 as an LTS release with five years of maintenance. Compare that stated horizon with your project’s support plans, target-platform coverage, compiler and build-system fit, and the specific APIs it uses. Separately confirm license entitlements and support requirements for your product’s configurations: the public LTS statement is not, on its own, a guarantee of a particular commercial support arrangement.
Keep Qt 5-to-Qt 6 porting advice in scope
Qt’s Porting to Qt 6 guide addresses the major-version transition from Qt 5, including deprecated or removed APIs and modules, and offers a Clazy-based porting tool. Those steps may still matter if your codebase retains Qt 5 compatibility code or is not fully migrated. They are not a blanket checklist of changes required when upgrading an application already maintained on Qt 6 to 6.12; Qt also documents changes for Qt 6 minor versions separately.
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