Hello! I recently started working with the Join API. I've often had problems with people don't understanding me, so I will describe the following as good as I can. An API (Application Programming Interface) let's one app call another. Join API is the part of Join that allows applications to send or retrieve data to it. The Join API uses, like many other APIs out there, API Keys. An API Key is a generated random piece of text, made to specify just YOUR account. With an API Key an application can get all your devices and call using groups. What this means is that they can change the clipboard/wallpaper and such on each and every one of your devices. This is why you should be careful with your API Key. Join luckily also allows you to reset and delete your API Key. If an application does something malicious, you can quickly cut them of to make sure they don't continue. When an application does get your API Key however, remember - there are still good applications out there, their most interesting thing to do would be to list your devices and let you pick one of them to send to. To send a message they don't use an API Key, but rather a Device ID. Unlike the API Key, before you click "Join API", you need to select the right device. This Device ID can not change. (It MIGHT be possible to delete and re-add your device, haven't tried) You don't need an API Key to send a message to one of your devices. This is what an application should be most interested of. With an API Key they can list your devices, choose one and get their ID. The ID is the main part in the API. With it they can change wallpaper and such. Continue if you now understand this and trust the application you are going to use it for. Open https://joinjoaomgcd.appspot.com/ If you only need the API Key you can choose whichever device you like.