Google OAuth Setup

This guide walks through creating a Google Cloud project and configuring OAuth. A single OAuth client handles both dashboard authentication and Google Calendar API access.

Token Expiration Warning

OAuth tokens expire every 7 days while your app is in "Testing" mode. You'll need to re-authenticate weekly unless you publish your app. This is a Google security measure for unpublished apps.

Quick Reference Checklist

Step 1: Create Google Cloud Project

Open Console

Go to Google Cloud Console

Create Project

Click the project dropdown at the top, then New Project

Name Project

Enter a name like Notion Calendar Sync and click Create

Select Project

Wait for creation, then select your new project from the dropdown

Step 2: Enable Google Calendar API

Open the Google Calendar API page
Click Enable

If the API is already enabled, you'll see "Manage" instead of "Enable". No action needed. Otherwise, wait a few seconds for confirmation before proceeding.

Go to APIs & Services > OAuth consent screen

Select User Type

Choose External (unless you have Google Workspace, then choose Internal) and click Create

Configure App Info

App name: Notion Calendar Sync
User support email: Your email
Developer contact email: Your email

Click Save and Continue through the remaining wizard steps until complete.

Add Scopes (After Creation)

After the consent screen is created:

Return to OAuth consent screen page
Click Edit App
Navigate to the Scopes section (or click "Add or Remove Scopes")
Add these scopes:

https://www.googleapis.com/auth/userinfo.email
https://www.googleapis.com/auth/userinfo.profile
https://www.googleapis.com/auth/calendar

You'll see "Your app requires verification" - ignore this. Verification is only required for apps with many external users. For personal use, no review is needed.

Click Save and Continue

The scopes section may not appear during initial setup. You can always add scopes by editing the consent screen after creation.

Step 4: Create OAuth Credentials

Go to APIs & Services > Credentials
Click Create Credentials > OAuth client ID
Select Web application
Enter name: Notion Calendar Sync Web

Authorised JavaScript origins

Add these URIs (replace your-app with your Vercel domain):

https://your-app.vercel.app

For local development, also add:

http://localhost:3000

Authorised redirect URIs

Add this URI (replace your-app with your Vercel domain):

https://your-app.vercel.app/api/auth/callback/google

For local development, also add:

http://localhost:3000/api/auth/callback/google

Click Create
Copy the Client ID and Client Secret

Keep your Client Secret secure. Never commit it to version control.

Step 5: Publish App (Recommended)

This step prevents weekly re-authentication. In "Testing" mode, OAuth tokens expire after 7 days, requiring you to sign in again.

To publish your app and get longer-lived tokens:

Go to the Auth Audience page
Under Publishing status, click Publish App
Confirm the warning about moving to production

What "Publishing" means:

For personal use: Google will show an "unverified app" warning once, but tokens won't expire weekly
No Google review required: Since you're the only user, no verification process is needed
Same functionality: Publishing doesn't change what your app can do

Staying in Testing Mode

If you prefer testing mode, just re-authenticate every 7 days. The While dashboard will show a warning when your token is approaching expiration.

Environment Variables

After completing this setup, you'll have:

Variable	Description	Your Value
	Your OAuth client ID
	Your OAuth client secret