License a game engine asset or mod

Written for developers

This is a step-by-step technical guide to adding a license screen to your product: it has code to copy and API calls to make. If you sell the product but don't write its code, read Not a developer? Start here and send this page to your developer.

This covers Unity editor tools and assets, Godot, Unreal, and game mods (Minecraft, Steam Workshop and similar). A license is usually per computer: the customer pastes the key once in an editor window or in-game menu, and the tool re-checks in the background.

Licensr does not host your asset or mod files. Host them on your own site or a marketplace page and link your buy page from there.

Product settings

Setting	Value
Activation mode	Seat: one activation per computer.
Client type	Native app. Game code sends no browser Origin.
Identifier	Unity: SystemInfo.deviceUniqueIdentifier. Elsewhere: a random ID you save once.

Create a plan

In the admin panel, open your product and add a plan: one price with a limit on how many devices or websites one key can be used on. Keep the defaults if you are unsure. You can add more plans later. See the Quick start.

Also create a Client API key on the product (shown once, starts with pk_test_ or pk_live_). This is the key you put in your product.

Get a test license

You do not have to pay to try your integration. In the admin panel go to Customers → Issue license, enter your own email, pick the product and plan, and issue it. The key (starts with lic_) arrives by email and is shown once on screen. The dashboard checklist has a shortcut for this.

Use your pk_test_ key against https://api.staging.licensr.app while you build, then switch to pk_live_ and https://api.licensr.app when you release.

What your license screen must do

Your product needs one small screen: a text box for the key, an Activate button, and a Deactivate button. It follows these rules, whatever the platform:

1. Activate, then validate. When the customer clicks Activate, call activate (this registers the device or website against the plan's limit), then validate. Unlock only if the validate response has valid: true. Save the key and the activation_id from the activate response.
2. Check again in the background. Call validate at every launch and about once a day while the product runs. A refund, a cancelled subscription, or an expired license happens after the sale, and this daily check is how your product finds out. Without it, a refunded key keeps working forever.
3. Lock immediately on valid: false. If Licensr cannot be reached, stay unlocked (optionally lock after a few days with no answer). Try again later.
4. Offer a Deactivate button. It calls deactivate with the saved activation_id, forgets the key, and locks the product. This lets a customer move to a new computer without asking you for help.

Messages to show when activate fails (read detail.error in the response):

Code	Say
license_not_found	"We could not find that key. Check for typos."
activation_cap_exceeded	"This key is already in use on the maximum number of devices. Deactivate it on another device first."
license_inactive	"This license is no longer active. Contact the seller."
no response at all	"Could not reach the license server. Try again."
any other code	"Something went wrong (code)." Show the code so the customer can send it to you.

The full list is in Errors.

Unity

Use the C# SDK (UPM git URL, plus the BouncyCastle package). Put the license screen in an EditorWindow for editor tools, or a menu for shipped games.

using Licensr.Sdk;
using UnityEngine;

public static class MyAssetLicense
{
    static readonly LicensrClient Client = new LicensrClient(new LicensrClientConfig
    {
        ApiKey = "pk_live_...",          // Client key, safe to ship
        PluginSlug = "my-asset",
        DeviceId = SystemInfo.deviceUniqueIdentifier,
    });

    // Customer clicked "Activate".
    public static async System.Threading.Tasks.Task<string> Activate(string licenseKey)
    {
        try
        {
            var activation = await Client.ActivateAsync(new ActivateRequest
            {
                LicenseKey = licenseKey,
                ActivationType = ActivationType.Seat,
                Identifier = SystemInfo.deviceUniqueIdentifier,
                Label = SystemInfo.deviceName,
            });
            var check = await Client.ValidateAsync(new ValidateRequest { LicenseKey = licenseKey });
            if (!check.Valid) return "This license is not active.";
            PlayerPrefs.SetString("licensr_key", licenseKey);
            PlayerPrefs.SetString("licensr_activation", activation.ActivationId);
            return null; // success
        }
        catch (LicensrApiException e) when (e.Code == "activation_cap_exceeded")
        {
            return "This key is already used on the maximum number of computers.";
        }
        catch (LicensrApiException) { return "We could not activate that key."; }
        catch (LicensrNetworkException) { return "Could not reach the license server."; }
    }

    // Call at editor load (pass true if a key is saved) and again about once a day (pass the current state).
    public static async System.Threading.Tasks.Task<bool> StillValid(bool previous)
    {
        var key = PlayerPrefs.GetString("licensr_key", "");
        if (key == "") return false;
        try { return (await Client.ValidateAsync(new ValidateRequest { LicenseKey = key })).Valid; }
        catch (System.Exception) { return previous; } // offline, rate limited or server error: keep the previous state
    }

    // Customer clicked "Deactivate".
    public static async System.Threading.Tasks.Task Deactivate()
    {
        var key = PlayerPrefs.GetString("licensr_key", "");
        var activation = PlayerPrefs.GetString("licensr_activation", "");
        if (key != "" && activation != "")
        {
            try { await Client.DeactivateAsync(new DeactivateRequest { LicenseKey = key, ActivationId = activation }); }
            catch (LicensrNetworkException) { }
        }
        PlayerPrefs.DeleteKey("licensr_key");
        PlayerPrefs.DeleteKey("licensr_activation");
    }
}

In the editor, PlayerPrefs is stored per Unity user account on the computer, which fits a per-computer license. The WebGL build target needs a custom transport (see the SDK page).

Godot

Godot with the .NET build can use the same C# code (replace the SystemInfo and PlayerPrefs calls with OS.GetUniqueId() and a ConfigFile). With GDScript, use HTTPRequest and follow the any-language guide.

Unreal, Minecraft, and other mods

Call the three HTTPS endpoints from your language (C++ with the C++ SDK, Java with java.net.http.HttpClient, and so on). The any-language guide has the exact requests. Mods usually run on the player's machine with no browser involved, so Native app is the right client type.

Link your buy page

Licensr does not host your download. Host the file on your own website or store, then add a Buy button that links to your Licensr buy page (the dashboard shows the full link, which looks like /buy/your-slug). Customers pay there and get their key by email, then paste it into your license screen.

Go live

1. Swap your pk_test_ key for the pk_live_ key and use https://api.licensr.app in the release build.
2. Buy your own product once, using the buy page, to see the whole flow.
3. Check the dashboard: the Get started checklist shows You're live! when payments, a product, a plan, a test license, and a first check from your product are all done.

Stuck? The license calls guide lists every field and error.