How to use ngrok (or other localhost tunnelling software) to test callback handlers

Run ngrok or some other localhost tunneling software. 

We'll use ngrok for our example, as it's relatively easy to setup.

Once you have ngrok up and running, it'll look like this:

We recommend using https as it's more secure.

1. Log in to app.sign.dropbox.com with your development account credentials.
2. Hover over your email address in the upper-right corner and click Settings > API. Here you can retrieve your API key.
3. Place the ngrok.io URL value into the Account Callback box, and click TEST. If your callback handler is setup correctly, you'll see the success message below: