How to use Postman with Google Cloud Platform APIs

This is a brief guide on how you can use Postman with Google Cloud Platform APIs, by connecting your Postman to Google using OAuth 2.0.

api-call-success

Create Access Token in Google Cloud Platform

In API & Services > Credentials > Create OAuth client ID

gcp-create-oauth-api-key

Add this under Authorized redirect URIs in your Google Console settings (https://console.cloud.google.com/apis/credentials/oauthclient).

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Set your Postman with one of the following callback URI/ redirect URI to:

Postman callback URI/ redirect_uri: https://www.getpostman.com/oauth2/callback
Postman callback URI/ redirect_uri: https://oauth.pstmn.io/v1/callback

Please take note of the callback URI/s that you have set, as we want to later make sure it matches what we have set in Postman.

gcp-create-oauth-api-key-redirect

Set up Postman to use Google Cloud Platform APIs

Create a new "Authorization" in Postman.

Fill in your Authorization details and click "Get New Access Token" when you are ready.

Type: OAuth 2.0
Add auth data to: Request Headers
Token name : Give the token a name, such as "GCP Token"
Grant Type: Authorization Code
Callback URL/ redirect_uri: Set this to one of the redirect URIs you set earlier in Google.
- https://www.getpostman.com/oauth2/callback
- https://oauth.pstmn.io/v1/callback
Auth URL: https://accounts.google.com/o/oauth2/auth
Access Token URL: https://accounts.google.com/o/oauth2/token
Scope: https://www.googleapis.com/auth/cloud-platform

If you were using Google Workspace, it would be something like this (changing the scope to the API function you are using): https://www.googleapis.com/auth/apps.groups.settings
Client ID: your-specific-clientid-fromgooglecloud.apps.googleusercontent.com
Client Secret: your-client-secret

postman-gcp-configuration

When you click on "Get New Access Token" you will be asked to authorize Postman to interface with Google's APIs.

So it will pop up a popup window and you will be asked to log into your Google account. Log in with your Google account used to access your Google Cloud Platform.

This process will generate a OAuth ID and Google will check that the request came from an authorized redirect URL (which we have set).

You will receive an "Authentication complete" message when it is successful. Click Proceed afterwards.

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Select "Use Token" to start using your new Access Token.

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This will add the Access Token under "Current Token> Access token> Available Tokens" to your Postman environment.

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You're all set. You can now run your Google Cloud Platform API calls.

Have fun using it now!

Example Google Cloud API call

Here is an example, using a Google Cloud Platform API call:

Google Cloud API Method: instances.list

GET https://compute.googleapis.com/compute/v1/projects/{project}/zones/{zone}/instances

where

project = your GCP project name (which you can get from your GCP URL)
zone = your GCP zone (which you can get from your GCP URL from your instance)

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postman-test-apis-instance

Troubleshooting:

Authentication failed

Couldn't complete authentication. Check the Postman Console for more details.

Authorisation Error
Error 400: redirect_uri_mismatch

Authorization Error
Error 400: redirect_uri_mismatch
You can't sign in to this app because it doesn't comply with Google's OAuth 2.0 policy. \n\nIf you're the app developer, register the redirect URI in the Google Cloud Console.

Solution:

In API & Services -> Credentials create an OAuth 2.0 client ID

Add one of the following redirect URI/ callback URI under "Authorized redirect URIs" in your Google Console settings (https://console.cloud.google.com/apis/credentials/oauthclient).

That is: redirect_uri:

You only need to set up one, so you can set any of URI you would like to set.

(Optional) Google Cloud Platform - Try this API

Google Cloud Platform offers this useful "Try this API" function on their API documentation pages. This is helpful when you are unsure if it is the variable values you are using that is causing API calls to fail. So while it is not available for all APIs, when it is available you can populate it with the minimum required details and then test that the variable values that you want to test works first. Then you can put it into Postman and/or scripts or the application you are building that will leverage the APIs.

To use this function.

Go to Google Cloud Platform > Compute Engine> Documentation> Reference > GET Method: instances.list API documentation page.

It is available on the far right, with the words "Try it!"

Then you populate it with basic details which you can then use to make a Google Cloud Platform API call. So once you are ready, click "Execute".

We will populate this with:

project = your GCP project name (which you can get from your GCP URL)
zone = your GCP zone (which you can get from your GCP URL from your instance). This will be for example, us-central1-a, us-central1-b, etc.