License an audio plugin

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.

Audio plugins are licensed per computer. The customer pastes their key in your plugin's editor window, the plugin activates that machine, and it re-checks in the background. This guide uses the C++ SDK, which has no third-party dependencies and is safe to use next to other plugins in the same host.

Licensr does not host your installer. Host it on your own website and link your buy page from there.

Product settings

Setting	Value
Activation mode	Seat: one activation per computer.
Client type	Native app. Plugins send no browser `Origin`.
Identifier	The computer's ID from `licensr::compute_hardware_id` (a hash, the raw ID never leaves the machine).

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:

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.
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.
Lock immediately on valid: false. If Licensr cannot be reached, stay unlocked (optionally lock after a few days with no answer). Try again later.
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.

Never call Licensr from the audio thread

All SDK calls are asynchronous and run on a background thread. On the audio thread, read client.snapshot() instead. It never blocks.

The code

Install the SDK with CMake (see the C++ SDK page), then:

#include <licensr/licensr.h>
#include <licensr/hwid.h>

licensr::ClientConfig config;
config.api_key = "pk_live_...";   // Client key, safe to ship in the plugin
config.plugin_slug = "my-plugin";

// A stable ID for this computer. Fall back to a UUID you saved yourself.
const std::string deviceId =
    licensr::compute_hardware_id(config.plugin_slug).value_or(loadOrCreateSavedUuid());
config.device_id = deviceId;

licensr::Client client(config);

// Customer clicked "Activate". Activate first, then validate.
void onActivateClicked(const std::string& licenseKey) {
  licensr::ActivateRequest request;
  request.license_key = licenseKey;
  request.activation_type = licensr::ActivationType::kSeat;
  request.identifier = deviceId;
  request.label = "My computer";

  client.activate(request, [licenseKey](licensr::Result<licensr::ActivateResult> activated) {
    if (!activated.ok()) {
      showMessage(activated.error().code);  // for example "activation_cap_exceeded"
      return;
    }
    const std::string activationId = activated.value().activation_id;
    client.validate(licenseKey, [licenseKey, activationId](licensr::Result<licensr::ValidateResult> checked) {
      if (checked.ok() && checked.value().valid) {
        saveLicense(licenseKey, activationId);  // your own storage
        unlock();
      } else {
        showMessage("This license is not active.");
      }
    });
  });
}

// At plugin load, and again from a timer about once a day.
void checkInBackground() {
  auto saved = loadLicense();
  if (!saved) return;
  client.validate(saved->key, [](licensr::Result<licensr::ValidateResult> checked) {
    if (!checked.ok()) return;  // offline or server trouble: keep the plugin unlocked
    if (!checked.value().valid) lock();
  });
}

// Customer clicked "Deactivate".
void onDeactivateClicked() {
  auto saved = loadLicense();
  if (!saved) return;
  client.deactivate(saved->key, saved->activationId, [](licensr::Result<licensr::DeactivateResult>) {
    forgetLicense();
    lock();
  });
}

// On the audio thread, only ever do this:
bool isLicensed() {
  auto snapshot = client.snapshot();
  return snapshot && snapshot->valid;
}

The SDK callbacks run on a background thread. Hop to your UI thread before touching the editor (in JUCE, use juce::MessageManager::callAsync).

Using JUCE? The optional licensr_juce module ships a ready-made LicenseActivationComponent with the key box and Activate button. See the JUCE module README and the demo plugin.

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

Swap your pk_test_ key for the pk_live_ key and use https://api.licensr.app in the release build.
Buy your own product once, using the buy page, to see the whole flow.
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.

Product settings​

Create a plan​

Get a test license​

What your license screen must do​

The code​

Link your buy page​

Go live​