{"id":8516,"date":"2025-12-15T06:12:03","date_gmt":"2025-12-15T06:12:03","guid":{"rendered":"https:\/\/studysection.com\/blog\/?p=8516"},"modified":"2025-12-15T06:12:03","modified_gmt":"2025-12-15T06:12:03","slug":"jwt-authentication-in-express-js","status":"publish","type":"post","link":"https:\/\/studysection.com\/blog\/jwt-authentication-in-express-js\/","title":{"rendered":"JWT Authentication in Express.js"},"content":{"rendered":"

Authentication is a critical part of nearly every web application. One of the most popular methods today is using JWT (JSON Web Tokens) \u2014 a compact, secure way to verify user identity without storing session data on the server.
\nWe’ll walk through how to implement JWT-based authentication in a Node.js<\/a> + Express.js<\/a> app.<\/p>\n

Step 1: Set Up Your Express Project<\/strong>
\nFirst, create Node.js project using the below commands:<\/p>\n

mkdir jwt-auth-demo && cd jwt-auth-demo\r\nnpm init -y\r\nnpm install express jsonwebtoken dotenv<\/code><\/pre>\n
You may also want to install nodemon for automatic server reloads during development.<\/p>\n
Step 2: Create Basic Server Structure<\/strong>
\nCreate a file named index.js file and also create a basic server:<\/p>\n
  \/\/ index.js\r\n  import express from 'express';\r\n  import dotenv from 'dotenv';\r\n\r\n  dotenv.config();\r\n  const app = express();\r\n  app.use(express.json());\r\n\r\n  const PORT = process.env.PORT || 3000;\r\n  app.listen(PORT, () => console.log(`Server running on port ${PORT}`));<\/code><\/pre>\n
Make sure to create a .env file:<\/p>\n
PORT=3000\r\nJWT_SECRET=mySuperSecretKey<\/code><\/pre>\n
Step 3: Generate JWT on Login<\/strong>
\nLet\u2019s assume a basic login system. You\u2019ll typically verify user credentials from a database. For simplicity, we\u2019ll hard-code a dummy user.<\/p>\n
\/\/ authController.js\r\n\r\n import jwt from 'jsonwebtoken';\r\n\r\n export const login = (req, res) => {\r\n    const { email, password } = req.body;\r\n    \/\/ Mock user check \u2014 in real apps, validate against DB\r\n    if (email === 'test@example.com' && password === 'password123') {\r\n        const token = jwt.sign(\r\n            { userId: '12345', email },\r\n            process.env.JWT_SECRET,\r\n            { expiresIn: '1h' }\r\n        );\r\n\r\n        return res.json({ success: true, token });\r\n    } else {\r\n        return res.status(401).json({ success: false, message:   'Invalid credentials' });\r\n    }\r\n };<\/code><\/pre>\n
Now set up a route for login:<\/p>\n
\/\/ routes.js\r\n    import express from 'express';\r\n    import { login } from '.\/authController.js';\r\n   \r\n    const router = express.Router();\r\n   \r\n    router.post('\/login', login);\r\n   \r\n    export default router;\r\n   \r\n    Update index.js to use the route:\r\n    import routes from '.\/routes.js';\r\n    app.use('\/api', routes);<\/code><\/pre>\n
Step 4: Create JWT Middleware to Protect Routes<\/strong>
\nThis middleware will verify the token and attach user info to the request:<\/p>\n
\/\/ middleware\/userAuth.js\r\n    import jwt from 'jsonwebtoken';\r\n   \r\n    const userAuth = (req, res, next) => {\r\n        const authHeader = req.headers.authorization;\r\n   \r\n        if (!authHeader || !authHeader.startsWith('Bearer ')) {\r\n            return res.status(401).json({ success: false, message: 'Unauthorized' });\r\n        }\r\n   \r\n        const token = authHeader.split(' ')[1];\r\n   \r\n        try {\r\n            const decoded = jwt.verify(token, process.env.JWT_SECRET);\r\n            req.user = decoded;\r\n            next();\r\n        } catch (err) {\r\n            return res.status(403).json({ success: false, message: 'Invalid or expired token' });\r\n        }\r\n    };\r\n   \r\n    export default userAuth;<\/code><\/pre>\n
Step 5: Protect Routes Using the Middleware<\/strong>
\nAdd a protected route that only logged-in users can access:<\/p>\n
 \/\/ routes.js\r\n    import userAuth from '.\/middleware\/userAuth.js';\r\n   \r\n    router.post('\/testing', userAuth, (req, res) => {\r\n        res.json({ success: true, message: `This is a testing Route.` });\r\n    });<\/code><\/pre>\n
Step 6: Test the API<\/strong><\/p>\n
    \n
  1. Login by sending a POST request to \/api\/login with valid credentials:<\/li>\n<\/ol>\n
    {\r\n    \"email\": \"test@example.com\",\r\n    \"password\": \"password123\"\r\n    }<\/code><\/pre>\n
      \n
    1. Copy the returned token.<\/li>\n
    2. Access protected route \/api\/testing by adding the token in the request header:<\/li>\n<\/ol>\n
      Authorization: Bearer
      \nIf the token is valid, you\u2019ll get a valid response.<\/p>\n
      Summary<\/strong>
      \nJWT authentication in Express.js is a powerful and scalable way to protect your APIs. By storing user information securely in the token and verifying it on each request, you eliminate the need for traditional server-side session handling.<\/p>\n","protected":false},"excerpt":{"rendered":"
      Authentication is a critical part of nearly every web application. One of the most popular methods today is using JWT<\/p>\n","protected":false},"author":1,"featured_media":8517,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6],"tags":[],"acf":[],"yoast_head":"\nJWT Authentication in Express.js<\/title>\n<meta name=\"description\" content=\"JWT authentication in Express.js is a powerful and scalable way to protect your APIs. 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