Example of how to use ngrok (or other localhost tunnelling software) to test callback handlers

Updated Sep 29, 2025

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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:

Python ngrok

We recommend using https as it's more secure. The value highlighted is:

https://7b1fde64.ngrok.io

Navigate to sign.dropbox.com and log in to your development account. Hover over your email address in the upper right corner and click Settings > API.

That's how you've retrieved your API Key, and this is where you'd setup your API Apps as well. It's this url if you're already logged in:

https://www.hellosign.com/home/myAccount#api

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:

Callback success message

If you want to continue receiving callbacks to that URL, make sure to click Save at the bottom of the page.

If you received an error, keep in mind that the two things Dropbox Sign looks for is a 200 response with the string "Hello API Event Received" somewhere in the body.

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