Install SimConnect correctly for MSFS 2020/2024, FSX and Prepar3D, choose the right legacy runtime, and fix common connection errors.
For Microsoft Flight Simulator 2020/2024, FSX and Prepar3D, SimConnect is normally installed with the simulator; do not download a random standalone copy. Install an extra legacy runtime only when an add-on specifically requires it, using the simulator’s own redistributable installer or the add-on’s prerequisites package.
Which SimConnect version do I need?
Use the SimConnect generation requested by the add-on rather than assuming the newest one replaces every older client. SimConnect versions are designed to coexist, so an older application may need its original runtime alongside the simulator’s native interface.
| Simulator | Already included | Possible extra requirement |
|---|---|---|
| Microsoft Flight Simulator 2020/2024 | SimConnect is built into the Windows PC simulator | A legacy FSX client only when required by an older external application |
| FSX boxed or Steam Edition | The native FSX interface | RTM, SP1 or XPACK legacy clients used by particular add-ons |
| Prepar3D | The interface matching the installed Prepar3D release | An older Prepar3D or FSX-compatible client from the supplied redistributables |
The SimConnect runtime lets an application communicate with the simulator. The SimConnect SDK contains headers, libraries, documentation and samples for developers; ordinary add-on users do not need the full SDK.
How do I install SimConnect?
Start with the simulator’s normal installation, then add only the runtime named by the software that cannot connect.
- Check the add-on requirements. Look for a named simulator generation such as FSX SP1, XPACK or a particular Prepar3D interface. If the developer supplies a prerequisites installer, use that package.
- Run the simulator once. Complete its installation or repair process and load a flight before troubleshooting an external application. This confirms that the simulator itself is working.
- Choose the correct installation route.
- For MSFS 2020 or 2024, there is normally nothing separate to install. If its built-in interface appears damaged, follow our MSFS SimConnect repair procedure rather than replacing DLL files manually.
- For FSX: Steam Edition, use the Microsoft installers supplied under its SDK and
LegacyInterfacesfolders. Our FSX: Steam Edition runtime instructions identify the legacy-client folders and installation order. - For boxed FSX, use the runtime included with the simulator, its SDK media or the add-on’s prerequisites package. If the expected SDK folders are absent, see how to restore the FSX SDK components.
- For Prepar3D, use the appropriate
SimConnect.msibeneath the simulator’sredist\Interfacefolder when a legacy client is required. Folder contents vary by Prepar3D release, so match the interface requested by the add-on.
- Close the simulator and run the MSI. Approve the Windows installation prompt and select repair if that runtime is already present. Do not uninstall other SimConnect versions merely to install this one.
- Restart and test locally. Load a flight, then start the external application. A Windows reboot is rarely necessary, but both applications must be restarted after changing a runtime.
Why does an add-on still say SimConnect is missing?
A continuing SimConnect error usually means the wrong legacy client was installed, the application is incompatible, or a remote connection has not been configured.
- Wrong runtime: an FSX-era application may require RTM, SP1 or XPACK specifically. Installing only the latest-looking package does not satisfy every older dependency.
- DLL copied by hand: do not place downloaded copies of
SimConnect.dllin the simulator directory, Windows system folders or another application’s directory. Use the official MSI. Leave DLL files deliberately supplied inside an add-on’s own folder untouched. - Damaged installation: rerun the relevant MSI and choose repair, or repair the simulator client. Removing every SimConnect entry can break add-ons that were already working.
- Remote-computer failure: the server address, protocol and port must agree on both computers, and the firewall must allow the connection. Our Prepar3D local and network setup guide covers the required configuration files.
- Unsupported application: a runtime cannot make an add-on built for another simulator or processor architecture compatible. Obtain the correct build of the add-on instead.
Do I need SimConnect.xml or the SDK?
A normal add-on running on the same PC usually needs neither manual configuration nor the SDK. Creating configuration files unnecessarily is a mistake we see often and can override a working default connection.
Networked applications may require a server-side SimConnect.xml and a client-side SimConnect.cfg, depending on the simulator and application. Developers compiling their own software need the SDK matching their target interface as well as the runtime.
These installation steps apply to Windows PCs. Xbox and PlayStation editions cannot run Windows SimConnect MSI packages or ordinary desktop add-ons.