Add-in Registration

External commands and external applications need to be registered in order to appear inside Revit. They can be registered by adding them to a .addin manifest file.

The order that external commands and applications are listed in Revit is determined by the order in which they are read in when Revit starts up.

Manifest Files

Revit API applications are registered with Revit via a .addin manifest file. Manifest files are read automatically by Revit when they are placed in one of two locations on a user's system:

In a non-user-specific location in "application data":

• C:\ProgramData\Autodesk\Revit\Addins\Revit 2018\

In a user-specific location in "application data":

• C:\Users<user>\AppData\Roaming\Autodesk\Revit\Addins\Revit 2018\

All files named .addin in these locations will be read and processed by Revit during startup. All of the files in both the user-specific location and the all users location are considered together and loaded in alphabetical order. If an all users manifest file shares the same name with a user-specific manifest file, the all users manifest file is ignored. Within each manifest file, the external commands and external applications are loaded in the order in which they are listed.

A basic file adding one ExternalCommand looks like this:

<?xml version="1.0" encoding="utf-8" standalone="no"?>
<RevitAddIns>
        <AddIn Type="Command">
                <Assembly>c:\MyProgram\MyProgram.dll</Assembly>
                <AddInId>76eb700a-2c85-4888-a78d-31429ecae9ed</AddInId>
                <FullClassName>Revit.Samples.SampleCommand</FullClassName>
                <Text>Sample command</Text>
                <VendorId>ADSK</VendorId>
                <VendorDescription>Autodesk, www.autodesk.com</VendorDescription> 
                <VisibilityMode>NotVisibleInFamily</VisibilityMode>
                <Discipline>Structure</Discipline>
                <Discipline>Architecture</Discipline>
                <AvailabilityClassName>Revit.Samples.SampleAccessibilityCheck</AvailabilityClassName>
                <LongDescription>
                        This is the long description for my command.
                        This is another descriptive paragraph, with notes about how to use the command properly.
                </LongDescription>
                <TooltipImage>c:\MyProgram\Autodesk.png</TooltipImage>
                <LargeImage>c:\MyProgram\MyProgramIcon.png</LargeImage>
        </AddIn>
</RevitAddIns>

A basic file adding one ExternalApplication looks like this:

<?xml version="1.0" encoding="utf-8" standalone="no"?>
<RevitAddIns>
<AddIn Type="Application">
                <Name>SampleApplication</Name>
                <Assembly>c:\MyProgram\MyProgram.dll</Assembly>
                <AddInId>604B1052-F742-4951-8576-C261D1993107</AddInId>
                <FullClassName>Revit.Samples.SampleApplication</FullClassName>
                <VendorId>ADSK</VendorId>
                <VendorDescription>Autodesk, www.autodesk.com</VendorDescription>
</AddIn>
</RevitAddIns>

A basic file adding one DB-level External Application looks like this:

<?xml version="1.0" encoding="utf-8" standalone="no"?>
<RevitAddIns>
<AddIn Type="DBApplication">
                <Assembly>c:\MyDBLevelApplication\MyDBLevelApplication.dll</Assembly>
                <AddInId>DA3D570A-1AB3-4a4b-B09F-8C15DFEC6BF0</AddInId>

                <FullClassName>MyCompany.MyDBLevelAddIn</FullClassName>

                <Name>My DB-Level AddIn</Name>                    
                <VendorId>ADSK</VendorId>
                <VendorDescription>Autodesk, www.autodesk.com</VendorDescription>
</AddIn>
</RevitAddIns>

Multiple AddIn elements may be provided in a single manifest file.

The following table describes the available XML tags:

.NET Add-in Utility for manifest files

The .NET utility DLL RevitAddInUtility.dll offers a dedicated API capable of reading, writing and modifying Revit Add-In manifest files. It is intended for use from product installers and scripts. Consult the API documentation in the RevitAddInUtility.chm help file in the SDK installation folder.

public void ManifestFile()
{
        //create a new addin manifest
        RevitAddInManifest Manifest = new RevitAddInManifest();

        //create an external command
        RevitAddInCommand command1 = new RevitAddInCommand("full path\\assemblyName.dll", 
        Guid.NewGuid(), "namespace.className", "ADSK");
        command1.Description = "description";
        command1.Text = "display text";

        // this command only visible in Revit MEP, Structure, and only visible 
        // in Project document or when no document at all
        command1.Discipline = Discipline.Mechanical | Discipline.Electrical |
                                Discipline.Piping | Discipline.Structure;
        command1.VisibilityMode = VisibilityMode.NotVisibleInFamily;

        //create an external application
        RevitAddInApplication application1 = new RevitAddInApplication("appName",
        "full path\\assemblyName.dll", Guid.NewGuid(), "namespace.className", "ADSK");

        //add both command(s) and application(s) into manifest
        Manifest.AddInCommands.Add(command1);
        Manifest.AddInApplications.Add(application1);

        //save manifest to a file
        RevitProduct revitProduct1 = RevitProductUtility.GetAllInstalledRevitProducts()[0];
        Manifest.SaveAs(revitProduct1.AllUsersAddInFolder + "\\RevitAddInUtilitySample.addin");
        }

public void ReadManifest()
{
        RevitProduct revitProduct1 = RevitProductUtility.GetAllInstalledRevitProducts()[0];

        RevitAddInManifest revitAddInManifest = 
     Autodesk.RevitAddIns.AddInManifestUtility.GetRevitAddInManifest(
          revitProduct1.AllUsersAddInFolder + "\\RevitAddInUtilitySample.addin");
}

Access to add-in data paths

Autodesk.Revit.ApplicationServices.Application.CurrentUsersAddinsDataFolderPath provides access to add-in data folder for the current Revit version and current user (such as %appdata%\Autodesk\Revit\Autodesk Revit 2025\AddinsData)