Effective September 2021, Dropbox will be deprecating long-lived access tokens.
This GIST generally describes how to authenticate requests to Dropbox API v2, for anyone working on a server-side PHP Dropbox implementation.
It's important to understand three types of codes you'll encounter:
- Access Code - this is a one-time code that represents user-granted app access.
- Access Token - this is short-lived token that provides access to Dropbox API endpoints.
- Refresh Token - this is a long-lived token that allows you to fetch a fresh Access Token.