"invalid_request: Unknown client" when attempting to get access token via Postman

I’m trying to connect to my auth0 protected expressjs API via Postman but am unable to obtain the initial token following the steps in the blog post.

I’ve triple checked that my settings match and I’m using the right variable values, but every time I try and get the initial token Auth0 instantly shows an “invalid_request: Unknown client” error.

How do I fix this? What setting have I missed? My web app works fine with this, both for user login and for secure API calls back to the server.

Hey there @neilenns ,

Did you implement steps from the blog for an SPA?
Which grant flow have you selected? Asking about the grant flow because I’m not sure but it might be that for an SPA app POSTMAN support only implicit grant flow.

The error refers to a Client ID of the application which asks for the access token on a user behalf.

Could you please try my advise on the grant flow and let me know?

Thanks for the reply Marcelina!

I just gave it a try again today and… it worked :man_facepalming: The grant type is set to “Authorization Code”. I’m not sure what I set it to yesterday when I was trying.

For future people finding this thread here’s a screenshot of my settings that worked since the blog post is from 2018 and doesn’t reflect the current Postman UI:

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Thanks for sharing a working setup @neilenns !

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