Configuration

Create APP at dropbox.com

Go to Developer area of dropbox.com

Simply visit: https://www.dropbox.com/developers

If this link is not valid anymore go to https://www.dropbox.com/, click the upper left menu icon with the 9 dots. Choose the App Center. In the left menu of the App Center you will find a link to Develop Apps. Now you should be in the developer corner of Dropbox.
Create new Dropbox App

Click the App Console button in the upper right corner. Now you see all your apps (if you have created some). Click the Create app button.
Choose API

With a free or simple Dropbox account you only have the possibility to choose the API with Scoped access. The TYPO3 Dropbox extension can only work with this API. Do not choose any other API.
Choose App type

For security reasons I prefer to choose App folder. But if you`re sure, you also can give your app full access to all of your Dropbox files.
Give it a name

Assign a Dropbox global unique name to your new app. Please consider, that words like dropbox are not allowed as part of the name.

Confirm your settings with button Create App. You will be redirected to detail view of your app.
Configure your new app

Switch over to tab Permissions and activate following permissions:
- files.metadata.read
- files.content.write
- files.content.read
Locate App key

For next section you will need to copy App key from tab Settings.

Create File Storage

Go to list module and choose PID 0 (Rootpage with TYPO3 logo in front).
Create a new record of type File Storage
On tab General choose a name like Dropbox
On tab Configuration you have to choose the Dropbox driver

Start Driver Wizard

While editing the File storage click on the + icon to start the wizard. Paste in the App Key from Dropbox App explained above. Click on Get AuthCode Link

On the next page you have to click on the authorization link which will open a new tab where you have to give access to your Dropbox App.

Copy the AuthCode from Dropbox page into the AuthCode field of the Wizard.

With a click on Get AccessToken a further request to dropbox.com will start in the background. On success the Refresh Token will automatically inserted in File Storage record and the wizard will close.

Save the record. On success it will show you some user data.

Performance

Note

At the bottom of the Configuration tab you will find the option: Folder for manipulated and temporary images etc. If you keep the default, all temporary images will be transferred over the Dropbox-API which is very slow. So it would be good to move that special folder to a folder on a fast file storage. Set this to 1:/_processed_/dropbox if your fileadmin file storage has the UID 1.

Attention

After changing the processed folder field to a local storage (f.e. 1 for fileadmin) you have to delete all sys_file_processedfile records where column "storage" is the UID of your dropbox storage (f.e. UID: 2). See: https://forge.typo3.org/issues/84069