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Google Authentication (OAuth)

⚙️ Setup¶

1️⃣ Add the following to your `.env.local` file (if not already done):¶

```bash NEXTAUTH_URL=http://localhost:3000 NEXTAUTH_SECRET= ````

NEXTAUTH_SECRET is a random string used to encrypt JWT tokens. It must be at least 15 characters long.

2️⃣ Create a new project in Google Cloud¶

Go to APIs & Services → Credentials
Click on [Configure Consent Screen]
Fill out the required information (Tip: Use ChatGPT to generate /tos and /privacy-policy pages).
Add userinfo.email and userinfo.profile to the scopes.
Add yourself as a test user.
Click Submit

3️⃣ Create OAuth credentials¶

Go to Credentials → [+ Create Credentials] → [OAuth Client ID]
Choose [Web Application]
Add the following to Authorized JavaScript origins:
http://localhost:3000
https://your-site.com
And add the following to Authorized redirect URIs:
http://localhost:3000/api/auth/callback/google
https://your-site.com/api/auth/callback/google

📌 If you’re using a subdomain like www, make sure to include it as well.

Click [Create]
Copy:
Client ID into GOOGLE_ID
Client Secret into GOOGLE_SECRET and paste them into your .env.local

4️⃣ Publishing and verification¶

Go to [OAuth Consent Screen] → click [Publish App] and submit your app for verification.
Click [Prepare for verification] and complete the required fields.
Google will send you an email—you need to respond to begin the process.
Your domain must be verified on Google Search Console. You can do that now.

You can now log in with Google on localhost.
It will also work in production, but a warning will appear until verification is complete (can take a few days).

6️⃣ Saving users in your database¶

The MongoDB adapter automatically saves new users when they log in via Google.
✅ Make sure your database is configured first.