At the beginning make sure you have your App key and App secret at hand from App Console page. Select desired application there and once got there in and scroll to field "App key" and "App secret" (for the secret "Show" should be used) keep the browser window accessible, so would be able take a look there when needed.
Next, open a new browser window and put into address line following:
https://www.dropbox.com/oauth2/authorize?token_access_type=offline&response_type=code&client_id=<App key>
Where "<App key>" is the one from you previous browser window. Next the confirmation you will get a code (alphanumeric sequence). The same could be received automatic when redirect URL is in use (either direct or PKCE code flow), but here we will perform it in such a way for clarity.
Next step will be to "materialize" the received code. In a terminal window execute following curl command:
curl https://api.dropbox.com/oauth2/token -d code=<received code> -d grant_type=authorization_code -u <App key>:<App secret>
Where "<received code>" is the code shown up in the second browser window after confirmation. "<App key>" and "<App secret>" come from the first browser window. As a result you will get in your terminal something like:
{"access_token": "sl.abcdefg123456789AbCdEf-GHijKLmn0U", "token_type": "bearer", "expires_in": 14400, "
refresh_token": "oDfT54975DfGh12345KlMnOpQrSt01a", "scope": "account_info.read files.content.read etc.", "uid": "123456789", "account_id": "dbid:ABCDEF5g8HijklMNopQ2Rs5tUV_wxy5z_YO4"}
Of course, you will receive different values filling the pattern. Here "sl.abcdefg123456789AbCdEf-GHijKLmn0U" is access token you can use in every regular API call for "14400" second since current moment until expires. "oDfT54975DfGh12345KlMnOpQrSt01a" is your refresh token. The one that will never expire (or till revoke).
When currently received access token expires, you can perform following curl call:
curl https://api.dropbox.com/oauth2/token -d grant_type=refresh_token -d refresh_token=oDfT54975DfGh12345KlMnOpQrSt01a -u <App key>:<App secret>
Where "oDfT54975DfGh12345KlMnOpQrSt01a" is the refresh token
Tutorial taken from Dropbox Forums written by Здравко
You can get Client ID and Client Secret App Console
Your data is saved locally!
Thank you Emulator.js for creating this emulator <3