Find your FSUIPC registration key in purchase records or an existing installation, and fix common version, name and email mismatches.
Your FSUIPC registration key is normally in the purchase-confirmation email or order history for the retailer account used to buy the licence. On a registered Windows installation, also look for an FSUIPC .key file in the module's installation folder. The free, unregistered version does not include or require a key.
This recovery process applies to FSUIPC generations used on Windows PC with Flight Simulator 2004, FSX, Prepar3D, Microsoft Flight Simulator 2020 and Microsoft Flight Simulator 2024. Desktop FSUIPC modules cannot be installed on Xbox or PlayStation consoles. If you are unsure why an add-on mentions it, see our explanation of what FSUIPC does and when it is needed.
How do I recover a lost FSUIPC key?
- Search your purchase email. Search every email account you may have used for “FSUIPC”, “registration” and the order receipt. The registered name and original email address are as important as the key itself.
- Check the retailer account. Sign in to the account through which you bought FSUIPC and inspect its order history, licence details and downloadable invoices. Downloading the free installer again will not generate or reveal a paid key.
- Inspect the working installation. Search Windows for
FSUIPC*.key. Preserve any matching file before uninstalling FSUIPC, moving the simulator or replacing the computer. - Request purchase recovery. If neither source is available, contact the original seller's order support with the order number, purchaser name, original email address, approximate purchase date and FSUIPC generation. Do not buy another licence until the old order has been checked.
Where is the FSUIPC key file stored?
The registration is generally stored in a .key file beside the active FSUIPC module or executable. Older FS2004, FSX and Prepar3D installations commonly keep it in the simulator's Modules directory; newer standalone FSUIPC generations use the installation folder selected during setup.
The filename follows the installed generation, so searching for FSUIPC*.key is safer than assuming one exact name. Files ending in .ini contain settings, while .log files contain diagnostic output; neither is a substitute for the registration file.
Copy the key file to a private backup before making changes. It can normally be opened with a plain-text editor to recover the registered identity and licence entry. Never post the file or its contents publicly.
Why is my FSUIPC registration key rejected?
An invalid-key message most often means that the key, registered identity or FSUIPC generation does not match the original purchase.
- Wrong major generation: a key bought for one named FSUIPC product does not automatically activate a later major generation. For example, an FSUIPC4 key should not be expected to register FSUIPC7.
- Name or email mismatch: enter the purchaser name and email or address exactly as issued, including an old email account that is no longer used.
- Wrong licence field: a separate WideFS key is not an FSUIPC registration key.
- Copy-and-paste errors: remove labels, line breaks and leading or trailing spaces without altering the key itself.
- Multiple installations: make sure you are registering or restoring the key file in the folder used by the FSUIPC copy that actually launches.
Do I need a key, and will an old one work?
Basic FSUIPC functionality is free and supports the interface used by many aircraft, utilities and other add-ons. A registration key unlocks the paid user facilities associated with that FSUIPC generation. Our FSUIPC download and licensing notes explain the distinction between free use and registered features.
An old key normally remains tied to the product generation named in its purchase record. Some purchases or upgrade arrangements may cover more than one named version, but the receipt or account entitlement is the deciding record.
An FSUIPC key is also completely separate from the simulator's activation code. If the missing licence is actually for Flight Simulator X, use our steps for locating or recovering an FSX product key instead.