To validate and activate licenses in the client side, you can use the Public REST API directly in your app. You can use this API anywhere, including desktop apps and browser extensions, with any programming language.
The first time a user opens your app, they should be prompted to activate their license. Here is how to make the HTTP request to activate a license.
The device identifier needs to be unique inside the license scope. You can use a MAC address, HWID, or any other type of identifier that is unique to a device.