What is FSUIPC? See which version fits FSX, Prepar3D and MSFS, what FSUIPC7 does, when registration is needed, and how to fix connection faults.
FSUIPC (Flight Simulator Universal Inter-Process Communication) is optional compatibility and interface software—an in-simulator module for FSX and Prepar3D, and a companion application for newer Microsoft Flight Simulator releases. It lets add-ons and hardware exchange data and commands. It is not the simulator itself, and normal FSX or Prepar3D operation does not require it.
What is FSUIPC and what does it actually do?
FSUIPC provides a common interface through which compatible software can read simulator data and send commands back to the simulator.
A client can read position, altitude, airspeed, fuel quantity, weather data and cockpit switch states. It may also operate controls or trigger simulator events. Much of this information is exposed through numbered data locations called offsets, giving add-on developers and hardware makers a predictable interface across supported simulators.
Typical clients include flight trackers, moving maps, ACARS programs, external instruments, hardware panels and home-cockpit systems. FSUIPC does not add aircraft, scenery or visual effects, and installing it without a specific purpose will not improve simulator performance.
Do you need FSUIPC for FSX or Prepar3D?
You need FSUIPC only when an add-on, external utility, hardware driver or control configuration specifically depends on it.
| Situation | Is FSUIPC needed? |
|---|---|
| Running default FSX or Prepar3D | No. Neither simulator requires it for normal operation. |
| Installing ordinary aircraft or scenery | Usually not. Install it only if the documentation names FSUIPC as a dependency. |
| Using a tracker, moving map or external instrument | Only if that program connects through FSUIPC. |
| Connecting cockpit hardware | Only if its driver requires FSUIPC, or if you choose FSUIPC for custom mappings. |
| Creating advanced axes, buttons and aircraft profiles | Optional, but these user-facing facilities generally require a registered licence. |
An FSUIPC requirement may apply to one feature rather than an entire aircraft. Read the dependency note carefully before assuming that either the simulator or every function in the add-on needs it.
Which FSUIPC version works with each simulator?
The correct branch is determined by the simulator generation and, for Prepar3D, whether it is a 32-bit or 64-bit release.
| Simulator | Architecture | FSUIPC branch | Key point |
|---|---|---|---|
| FSX boxed editions and FSX: Steam Edition | 32-bit | FSUIPC4 | Use the latest supported FSUIPC4 installer, not a DLL bundled with an old aircraft. |
| Prepar3D v1, v2 and v3 | 32-bit | FSUIPC4 | These releases belong to the same 32-bit branch as FSX. |
| Prepar3D v4, v5 and v6 | 64-bit | FSUIPC6 | FSUIPC6 is the maintained 64-bit Prepar3D branch. Older P3D v4 material may mention the legacy FSUIPC5 branch. |
| Microsoft Flight Simulator 2020 and Microsoft Flight Simulator 2024 on Windows PC | 64-bit | FSUIPC7 | FSUIPC7 runs as a separate Windows application rather than an in-simulator DLL. |
FSUIPC4 cannot load into 64-bit Prepar3D. For any Prepar3D release not explicitly named by an installer, check its official compatibility notes rather than assuming that a branch for an earlier version will work.
Our FSUIPC branch-selection and download guide helps identify the appropriate package. A mistake we see repeatedly is an old aircraft installer overwriting a newer working module with its bundled copy.
What is FSUIPC7?
FSUIPC7 is the branch for the Windows PC editions of Microsoft Flight Simulator 2020 and Microsoft Flight Simulator 2024.
Unlike FSUIPC4 and FSUIPC6, it is a separate application that communicates with the running simulator through SimConnect. It does not belong in the MSFS Community folder and should not be expected to appear as an FSX-style module in an in-simulator Add-ons menu.
FSUIPC7 cannot be installed on the Xbox Series X|S or PlayStation 5 and PS5 Pro console editions because it requires an external Windows program.
Is FSUIPC free, and where can you download it?
The unregistered FSUIPC interface is normally sufficient when a dependent add-on only needs to exchange data and commands with the simulator.
- Unregistered interface: generally enough for an aircraft, tracker, instrument program or hardware driver that simply says
FSUIPC required. - Registered licence: unlocks advanced user facilities such as detailed axis assignment and calibration, aircraft-specific profiles, and button or key programming.
For FSX, the free option is the unregistered FSUIPC4 interface. A manual must specifically require registered functions before you should assume that a paid licence is necessary. Registration keys can be tied to a major FSUIPC generation, so an older key should not be assumed to activate FSUIPC6 or FSUIPC7.
Use the latest developer-issued installer for the correct branch. Avoid standalone DLL files from third-party archives and legacy copies bundled inside aircraft packages; they may be outdated, incompatible or missing the installer logic needed to register the module correctly.
What do FSUIPC, SimConnect and WideFS requirements mean?
These names describe different requirements and should not be treated as interchangeable.
| Documentation says | What it usually means |
|---|---|
FSUIPC required | The add-on needs the FSUIPC interface. An unregistered installation is usually sufficient. |
Registered FSUIPC required | The product uses a paid user feature, such as FSUIPC control programming or profiles. |
SimConnect required | The software uses Microsoft's simulator connection API. Some programs connect directly through SimConnect and do not need FSUIPC. |
WideFS required | The client is designed to communicate with FSUIPC across a local network. WideFS is a separate networking component and may require separate registration. |
FSUIPC does not replace SimConnect. FSX and Prepar3D include SimConnect, although older clients sometimes require a particular legacy SimConnect runtime. Likewise, installing FSUIPC alone does not make a same-PC client work across two computers; the software must explicitly support WideFS or provide its own network connector.
How should you install FSUIPC in FSX or Prepar3D?
Install FSUIPC with the matching branch installer rather than manually copying a module from an old add-on package.
- Identify the simulator and architecture. Use FSUIPC4 for FSX, FSX: Steam Edition and 32-bit Prepar3D; use the supported 64-bit branch for later Prepar3D releases.
- Read the add-on requirement. Record any minimum FSUIPC build and whether the manual requires only the interface or registered user features.
- Back up customised settings. If you already use FSUIPC for controls, preserve its configuration files before upgrading or changing the installation.
- Close the simulator and connected clients. This prevents loaded files from remaining locked during the update.
- Run the correct installer. Let it detect or register the simulator. FSX-era modules and later Prepar3D add-on packages do not all use the same registration method.
- Approve the module if prompted. FSX may display a trusted-software prompt on first use. Rejecting it prevents FSUIPC from loading even though installation appeared to finish successfully.
- Load a flight and verify the module. Check for an FSUIPC entry in the simulator's Add-ons menu and inspect the FSUIPC log if the entry is absent.
- Start the dependent program. For the first test, wait until the simulator is fully loaded into a flight before connecting the client.
Our detailed FSX installation instructions cover the boxed and Steam editions. If your reason for registering is control management, use our guide to assigning and calibrating controls through FSUIPC rather than duplicating assignments in two places.
Why is an add-on still not connecting after FSUIPC is installed?
The most common causes are the wrong branch, a module that was installed but never loaded, an outdated build or a second missing dependency.
- Check the branch first. FSUIPC4 is not a substitute for a 64-bit Prepar3D branch, and FSUIPC7 is not the package for FSX.
- Confirm that it actually loaded. An installed file proves very little. Check the simulator's Add-ons menu and FSUIPC log for loading, trust or registration errors.
- Treat FSUIPC7 differently. It is an external program, so verify that the application is running and reports a simulator connection; do not look for an FSX-style DLL or place it in the MSFS Community folder.
- Remove stale duplicates. Do not leave incompatible modules registered for the same simulator or allow a legacy aircraft installer to downgrade a working copy.
- Meet the minimum build requirement. Some clients depend on offsets or functions introduced in later builds of the correct branch.
- Match Windows privilege levels. Running the simulator as administrator while the client runs normally, or the reverse, can obstruct communication. Use the same level unless the product documentation says otherwise.
- Check security software. Confirm that the installer, module or FSUIPC7 executable was not quarantined or blocked from running.
- Check other prerequisites. The add-on may also need a SimConnect runtime, background loader, network connector, WideFS configuration or its own connection settings.
Our FSUIPC connection troubleshooting guide covers the next checks when the module or client remains unavailable.
If controls twitch, trigger twice or refuse to centre after configuration, look for duplicate assignments. An axis mapped in both the simulator controls menu and FSUIPC receives competing inputs. Give each axis or button command a single owner.
What problems will FSUIPC not fix?
FSUIPC does not repair low frame rates, crashes caused by scenery, missing textures, invisible aircraft, broken gauges or incompatible panels.
Installing it as a general troubleshooting measure often sends the diagnosis in the wrong direction. Blank cockpit displays usually indicate gauge incompatibility, missing runtimes, blocked files or an incomplete aircraft installation—not the absence of FSUIPC unless the aircraft documentation explicitly identifies it as a dependency.