---
url: https://docs.sunlicense.com/how-to/dotnet-unity-tool.md
description: >-
  How to add license keys to a .NET app or a Unity editor tool - check the
  buyer's key with the SunLicense .NET SDK (netstandard2.0), stop on a
  rejection, keep working offline, and what the Unity Asset Store allows.
---

# How to add license keys to a .NET or Unity tool

**Short answer:** `dotnet add package SunLicense`, check the key at start-up with `ValidateAsync`, stop (or switch to
the free features) when SunLicense says no, and keep working when it can't be reached. The SDK targets
netstandard2.0, so the same code runs in .NET 6+, .NET Framework 4.7.2+, Mono and Unity.

```csharp
using SunLicense;

using var client = new SunLicenseClient("https://api.sunlicense.com", token: ApiKey);   // API key from your build
try
{
    var r = await client.ValidateAsync(licenseKey, new Dictionary<string, string> { ["host"] = MachineId() });
    if (r.StatusCode == 400)   // EXPIRED, REVOKED, TOO_MANY_MACHINES…: Body has the code
    {
        Console.Error.WriteLine($"License rejected: {r.Body}");
        return 1;
    }
}
catch (SunLicenseException e)
{
    Console.Error.WriteLine($"SunLicense can't be reached, running anyway: {e.Message}");
}
```

`ValidateAsync` returns `IsValid`, `StatusCode` and `Body`; it throws `SunLicenseException` only when SunLicense can't
be reached.

**Or let your AI agent do it:** paste the [setup prompt](https://sunlicense.com/prompt) into Claude Code, Cursor,
Codex or Copilot in your solution's folder.

Free plan: 3 products, 100 licenses, no credit card. [Create a free account](https://sunlicense.com/start?ref=docs-howto-dotnet).

## Step by step

1. **In the dashboard:** a product, a policy (for example *2 machines*) and an **API key**, which can only validate.
2. **Install:** `dotnet add package SunLicense`. In Unity, put `SunLicense.dll` (from the NuGet package's
   `lib/netstandard2.0`) in an `Editor/` or `Plugins/` folder.
3. **Your API key** goes in at build time (an MSBuild property written into a generated class, or a CI secret), never in
   the repository.
4. **The buyer's key:** a settings file in their app data folder (`Environment.SpecialFolder.ApplicationData`), or in a
   Unity editor tool `EditorPrefs.SetString("MyTool.License", key)` from a small activation window.
5. **Machine id** as `host`: hash `Environment.MachineName` with the OS and architecture; in Unity,
   `SystemInfo.deviceUniqueIdentifier` is already stable per machine. [Choosing a machine id](/guide/sdks#choosing-a-machine-id).
6. **Results:** 200 runs, 400 stops with the [reason](/guide/concepts#validation-result-codes) (mask keys in logs and
   UI), anything else runs and checks again later. Desktop users go offline: accept a recent good check, or hand out a
   signed [offline license file](/guide/offline-licenses).
7. **Reuse one client.** It wraps an `HttpClient`; create one per app (or pass your own `HttpClient` to the constructor).

## Unity editor tools

```csharp
[InitializeOnLoad]
static class MyToolLicense
{
    public static bool Active { get; private set; } = true;
    static MyToolLicense() => _ = Check();

    static async Task Check()
    {
        var key = EditorPrefs.GetString("MyTool.License", "");
        if (key == "") { Active = false; return; }
        using var client = new SunLicenseClient("https://api.sunlicense.com", token: ApiKey);
        try
        {
            var r = await client.ValidateAsync(key, new Dictionary<string, string> { ["host"] = SystemInfo.deviceUniqueIdentifier });
            Active = r.StatusCode != 400;
        }
        catch (SunLicenseException) { /* offline: stay active */ }
    }
}
```

Your menu items and windows check `MyToolLicense.Active`. Only the editor needs the check: tools that never go into the
player build don't ship it to the games your buyers make.

**Unity Asset Store:** its submission guidelines restrict DRM, registration and features locked behind a key, so a
package sold there shouldn't check a license. Use this for tools you sell yourself (itch.io, Gumroad, Lemon Squeezy,
Payhip, your own site), and read the current
[Asset Store submission guidelines](https://assetstore.unity.com/publishing/submission-guidelines) before you list.

## Going further

* [Protection](/guide/protection): seal part of the tool so a copy with the check removed has nothing to run.
* Selling a FiveM resource in C#? The same SDK works there; the [FiveM guide](/how-to/fivem-script) covers Tebex and escrow.
* More on [licensing game dev tools](https://sunlicense.com/for/game-dev-tools/) and
  [desktop apps](https://sunlicense.com/for/desktop-apps/).