Google Login in Express with PassportJS & JWT

In this blog, we will implement Google Authentication in an Express.js app using:

• TypeScript
• Express.js
• Mongoose
• Passport.js
• JWT Authentication

---

Project Structure

└── src/
    ├── config/
    ├── controllers/
    ├── middlewares/
    ├── models/
    ├── routes/
    ├── utils/
    ├── app.ts
    └── index.ts
├── .env
├── package.json
└── tsconfig.json

---

Install Required Packages

npm install passport passport-google-oauth20
npm install jsonwebtoken cookie-parser bcrypt mongoose

npm install -D @types/passport-google-oauth20

---

Create Google OAuth Credentials

Go to Google Cloud Console
{/*

https://console.cloud.google.com/

*/}

Steps

1. Create a new project

2. Configure OAuth Consent Screen

3. Create OAuth 2.0 Client ID

4. Configure OAuth Client

5. Copy Client ID and Client Secret

---

Environment Variables

Create a .env file:

GOOGLE_CLIENT_ID=
GOOGLE_CLIENT_SECRET=
GOOGLE_CALLBACK_URL=http://localhost:3000/api/v1/auth/google/callback

---

Important User Model Changes

Your user model MUST contain these fields:

refreshToken: {
  type: String,
},

googleId: {
  type: String,
},

If you already support password login, make password optional:

password: {
  type: String,
  required: false,
},

Also add checks wherever password login is used:

if (!user.password) {
  throw new Error("Password login not available for this account");
}

---

Configure PassportJS

Create: src/config/passport.ts

import passport from "passport";
import { Strategy as GoogleStrategy } from "passport-google-oauth20";
import { User } from "../models/User.model.js";
import { generateUsername } from "../utils/usernameGen.js";

passport.use(
  new GoogleStrategy(
    {
      clientID: process.env.GOOGLE_CLIENT_ID!!,
      clientSecret: process.env.GOOGLE_CLIENT_SECRET!!,
      callbackURL: process.env.GOOGLE_CALLBACK_URL,
    },
    async (_accessToken, _refreshToken, profile, done) => {
      try {
        const email = profile.emails?.[0]?.value;

        if (!email) {
          return done(new Error("No email found"));
        }

        let user = await User.findOne({
          $or: [{ googleId: profile.id }, { email }],
        });

        if (user && !user.googleId) {
          user.googleId = profile.id;
          await user.save();
        }

        const username = await generateUsername(profile.displayName);

        if (!user) {
          user = await User.create({
            username,
            fullName: profile.displayName,
            email,
            googleId: profile.id,
            avatarUrl: profile.photos?.[0]?.value || "",
          });
        }

        user = await User.findById(user._id).select(
          "-password -refreshToken -googleId"
        );

        if (!user) {
          return done(new Error("User not found after creation"));
        }

        return done(null, user);
      } catch (error) {
        return done(error as Error);
      }
    }
  )
);

export default passport;

---

Username Generator

Create: src/utils/usernameGen.ts

Your logic should:

• Convert full name into username
• Add numbers if username already exists
• Ensure uniqueness

Example:

john
john12
john123

---

Google Auth Controller

src/controllers/auth.controller.ts

export const googleAuth = async (req: Request, res: Response) => {
  const user = req.user!;

  const { accessToken, refreshToken } =
    await generateTokens(user._id);

  return res
    .status(200)
    .cookie("accessToken", accessToken, cookieOptions)
    .cookie("refreshToken", refreshToken, cookieOptions)
    .json({
      success: true,
      user,
    });
};

---

Google Auth Routes

src/routes/auth.route.ts

router.route("/google").get(
  passport.authenticate("google", {
    scope: ["profile", "email"],
    session: false,
  })
);

router.route("/google/callback").get(
  passport.authenticate("google", {
    failureRedirect: "/login",
    session: false,
    failureMessage: "Failed to login with Google",
  }),
  googleAuth
);

---

Initialize Passport

Inside app.ts

import passport from "./config/passport.js";

app.use(passport.initialize());

---

Authentication Flow

1. User visits: /api/v1/auth/google
2. Google login page opens
3. User authenticates
4. Google redirects back to callback URL
5. User gets JWT tokens
6. Cookies are set

---

Testing

Open: http://localhost:3000/api/v1/auth/google

If configured correctly:

• Google login opens
• User account gets created
• JWT cookies are generated

---

Common Issues

Invalid Redirect URI

Ensure callback URL matches exactly in:

• Google Console
• .env
• Passport Strategy

Missing Email

Make sure scope contains:

scope: ["profile", "email"]

---

Production Tips

Use secure cookies in production:

secure: true,
httpOnly: true,
sameSite: "strict",

---

Final Thoughts

You now have Google Authentication working with:

• Express.js
• TypeScript
• Mongoose
• Passport.js
• JWT

You can further extend this with:

• GitHub OAuth
• Discord OAuth
• Role-based auth
• Email verification

Happy coding 🚀