How can I resolve the Dropbox OAuth redirect URI error when integrating with n8n via Docker?

Below is an explanation of the issue and some guidance on how to resolve it:

What's Happening

When you first deploy n8n via Docker, the OAuth Redirect URL is automatically generated as:

  http://0.0.0.0:5678/rest/oauth2-credential/callback

Dropbox rejects this URL with the error message:

  “Non-local OAuth 2 redirect URIs may not start with “http:” or “javascript:””

This happens because Dropbox only accepts valid local URLs for OAuth redirection—typically starting with “http://localhost” (or a proper domain name). When you change the URL in Dropbox to:

  http://localhost:5678/rest/oauth2-credential/callback

Dropbox accepts it. However, if n8n still uses “0.0.0.0” internally for redirection, the mismatch can cause connection issues during the OAuth callback.

Why It Occurs

The error is Dropbox’s way of ensuring that non-local domains aren’t used for callback redirection. In your case:

• Using 0.0.0.0: This is a wildcard interface address and isn’t recognized as a valid “local” or “localhost” URL by Dropbox.
• Using localhost: Dropbox accepts this, but your running n8n instance must also “see” the redirect as coming from localhost.

How to Fix It

You’ll need to ensure consistency between the URL registered on Dropbox and the URL n8n uses for its webhook callback. Here’s what to do:

1. Set the Correct Webhook URL in n8n:

   When running n8n via Docker, define the environment variable WEBHOOK_URL to explicitly set the correct host portion. For example, update your Docker run command (or your Docker Compose file) to include:

   YAMLCopied
   environment:
     - WEBHOOK_URL=http://localhost:5678

   This ensures that n8n generates OAuth redirect URLs as http://localhost:5678/rest/oauth2-credential/callback.

2. Verify Dropbox Configuration:

   Make sure that the redirect URI entered in your Dropbox app settings exactly matches the one issued by n8n (which should be as set above). This avoids any mismatch that could result in runtime errors.

3. Confirm Your Deployment Settings:

   If you’re running n8n on a Mac Mini (self-hosted via Docker), ensure that there is no overriding configuration (or proxy settings) that inadvertently changes the host to “0.0.0.0”. The Docker container needs to be aware of the intended public URL.

Summary

The error message (“Non-local OAuth 2 redirect URIs may not start with “http:” or “javascript:””) indicates that Dropbox will not accept a callback URL starting with “http://0.0.0.0…” because it is not considered a valid local redirect URI. Switching to “http://localhost:5678” is correct, but you must also configure your n8n Docker instance (via the WEBHOOK_URL environment variable) so that the generated callback URL matches the one you’ve registered with Dropbox. This alignment should resolve the error during the OAuth connection process.

Feel free to ask if you need any further guidance!