Installing a Revit add-in,
properly.

Where add-ins live

Each add-in is a .addin XML manifest pointing at a DLL. Revit reads every manifest in these folders at start-up - one folder per Revit year, which is why an installer must put a copy in each year you use.

The “Security - Unsigned Add-In” dialog

Revit shows it for DLLs without a trusted code-signing certificate. It is a trust decision, not a malware verdict. Before clicking Always Load: download only from the vendor's site, and compare the installer's SHA-256 with the published checksum:

certutil -hashfile Parapet-Setup.exe SHA256

Parapet publishes checksums on the docs page.

.NET 8 and Revit 2025+

Revit 2025, 2026 and 2027 run add-ins on .NET 8; earlier versions on .NET Framework 4.8. A DLL built for one will not load in the other (“Could not load file or assembly…”). A vendor that lists 2020-2027 ships both builds - Parapet's installer picks the right one per year. More: Revit 2027 add-ins.

Installing Parapet specifically

Uninstalling cleanly

• Windows Settings → Apps → the add-in → Uninstall. Check the Addins\<year> folders for leftover .addin files.
• For licensed add-ins, deactivate the computer first so the seat is freed (Parapet: Licenses dialog or your account page).