CAD & architecture extensions

License key system for Revit add-ins, SketchUp extensions, and Rhino/Grasshopper plugins

There is no standard way to sell and license third-party Revit add-ins, SketchUp extensions, or Grasshopper plugins. Licensr gives AEC developers a turnkey license key system with machine-locked activation, Stripe payments, and a branded storefront — one REST API that works across every BIM and CAD platform.

WordPress Audio plugins Desktop apps Trading indicators Adobe plugins Figma plugins CAD & AEC Game engines Game mods Browser extensions Productivity VS Code

C# (Revit add-in)

// In your Revit ExternalApplication.OnStartup
public Result OnStartup(UIControlledApplication app)
{
    using var http = new HttpClient();
    var body = JsonSerializer.Serialize(new
    {
        license_key = Settings.LicenseKey,
        plugin_slug = "my-revit-addon",
    });
    var req = new HttpRequestMessage(HttpMethod.Post,
        "https://api.licensr.app/v1/license/validate")
    {
        Content = new StringContent(
            body, Encoding.UTF8, "application/json"),
    };
    req.Headers.Authorization =
        new AuthenticationHeaderValue("Bearer", API_KEY);

    var res = http.Send(req);
    var doc = JsonDocument.Parse(
        res.Content.ReadAsStream());

    if (!doc.RootElement
            .GetProperty("valid").GetBoolean())
    {
        TaskDialog.Show("License",
            "Invalid or expired license.");
        return Result.Failed;
    }
    return Result.Succeeded;
}

Compatible CAD, BIM & AEC platforms

Revit (C# / .NET)

SketchUp (Ruby)

Rhino / Grasshopper (C#/Python)

ArchiCAD (C++)

Vectorworks (Python)

Any REST language

Why AEC developers choose Licensr for plugin licensing

No standard license key system in AEC software

Revit, SketchUp, Rhino, ArchiCAD, and Vectorworks offer no built-in licensing for third-party developers. Licensr fills that gap with a complete license key system — validation, activation, Stripe payments, and a customer portal included.

Machine-locked license keys prevent firm-wide sharing

AEC add-ins and BIM tools often carry premium prices. Machine-locked activations prevent a single license key from being shared across an entire architecture firm without paying for additional seats.

Sell direct — no Autodesk App Store or marketplace fees

Your Revit add-in or SketchUp extension gets its own buy page. Architects and engineers pay via Stripe on your own account. No Autodesk App Store cut, no middleman.

One API for Revit, SketchUp, Rhino, ArchiCAD, and more

Whether your extension is written in C# for Revit, Ruby for SketchUp, Python for Rhino/Grasshopper, or C++ for ArchiCAD — the same REST call validates the license key. Use the official C# SDK for .NET hosts; other languages call the API directly.

Annual subscription billing handled automatically

Sell annual or monthly subscriptions that auto-renew via Stripe. When a subscription lapses, the validate call returns false — no manual revocation, no chasing expired licenses.

Official SDK

Official C# SDK: Revit, Rhino, and .NET CAD hosts

Licensr.Sdk targets netstandard2.1 so it drops into Revit add-ins, Rhino/Grasshopper plugins, and other .NET CAD hosts. Same REST surface for SketchUp (Ruby) and ArchiCAD (C++) via the raw API.

C# SDK docs All SDKs →

Validate.cs

$ dotnet add package Licensr.Sdk

using Licensr.Sdk;

var client = new LicensrClient(new() {
    ApiKey = "pk_live_...",
    PluginSlug = "my-synth",
});

var result = await client.ValidateAsync(new() {
    LicenseKey = userKey,
});
if (result.Valid) UnlockFullFeatures();

// → Valid = true, Entitlement = Full,
//   FeatureFlags = { "auto_backup": true }

Ready to license and sell your CAD extension?

Free tier available. From signup to a working license key validation in 15 minutes.

Start for free Read the docs