Getting the Callback URL

Log into the backend of the site you want to host the OAuth2 helpers.

Go to Components, Akeeba Backup for Joomla!, Control Panel.

Click on Options.

Click on the OAuth2 Helpers tab.

Set OAuth2 Helper for Dropbox to Yes. You will see a blue note with three URLs below. Copy the Callback URL. It looks something like this (line breaks added for clarity):

https://www.example.com/index.php?option=com_akeebabackup

&view=oauth2&task=step2&format=raw&engine=dropbox

Copy this URL. Please remember that you need to use this URL verbatim in a later step.

Click on the Close button, without saving the component options.

Creating the API application

Log into your Dropbox account.

Go to https://www.dropbox.com/developers and click on Create Apps.

Select Scoped access. Even if it's pre-selected for you, you still need to click on it to see the next step.

Select Full Dropbox.

Give your app a name.

Click on Create app.

You are taken to your application's settings page.

A Dropbox API app can be either in development or production status. In development mode there is a limit of up to 500 users, but you don't get pestered by app reviews. In production mode you can have a practically unlimited number of users, but you do have to complete app reviews. In the instructions below we assume that you will need less than 500 users, therefore you can remain in development mode.

Click on the Add more users button to raise the limit of users from 1 to 500.

Find Redirect URIs and paste the Callback URL you copied earlier. Then, click on the Add button next to it.

Click on the Permissions tab and select the following permissions:

Remember to click on the Submit link in the toast notification at the bottom of the window.

If you want, you can now set up some branding in the Branding tab.

Once you are done, go back to the Settings page.

Copy the App key. This is your Client ID.

Click on Show next to App Secret and copy the secret which appears. This is your Client Secret.

Enabling the custom OAuth2 Helper

Log into the backend of the site you want to host the OAuth2 helpers.

Go to Components, Akeeba Backup for Joomla!, Control Panel.

Click on Options.

Click on the OAuth2 Helpers tab.

Set OAuth2 Helper for Dropbox to Yes.

Paste the Client ID (App key) and Client Secret (App secret) you copied in the previous step into the same-named text boxes under the "OAuth2 Helper for Dropbox" section.

Click on Save & Close.

Getting the OAuth2 Helper and Refresh URLs

Log into the backend of the site which hosts the OAuth2 helpers.

Go to Components, Akeeba Backup for Joomla!, Control Panel.

Click on Options.

Click on the OAuth2 Helpers tab.

Find the OAuth2 Helper for Dropbox. You will see a blue note with three URLs below.

Copy the OAuth2 Helper URL and OAuth2 Refresh URL.

Telling Akeeba Backup to use a custom helper

Log into the backend of the site you will be taking the backups on. This may be different than the site which hosts the OAuth2 helpers.

Go to Akeeba Backup, select your backup profile, and click on Configuration.

Scroll down to the Post-processing Engine.

Select Upload to Dropbox

Change the OAuth2 Helper to Custom.

Paste the OAuth2 Helper URL and OAuth2 Refresh URL you copied in the previous step.

Click on Save. This is important! Until you click on Save, Akeeba Backup does not know you intend to use a custom OAuth2 Helper.

Authentication and setup

When the page reloads, click on Authentication - Start here.

Go through the authentication.

At the end, you will see an Access Token and a Refresh Token. Copy them into the respective fields of your Akeeba Backup profile.