node server not running in browser or in postman in terminal its fine

this is the server.js code

require('dotenv').config()
const express = require('express')
const mongoose = require('mongoose')
const cors = require('cors')
const cookieParser = require('cookie-parser')


const app = express()
app.use(express.json())
app.use(cors())
app.use(cookieParser())


//Routes
app.use('api', require('./routes/authRouter'))

const URI = process.env.MONGODB_URL
mongoose.connect(URI, {
    useCreateIndex: true,
    useFindAndModify: false,
    useNewUrlParser: true,
    useUnifiedTopology: true
}, err => {
    if(err);
    console.log('Connected to mongodb')
})


const port = process.env.PORT || 5000
app.listen(port, ()=> {
    console.log('server up and running', port)
})

authRouter code

const router = require('express').Router()
const authCtrl = require('../controllers/authCtrl')

router.post('/register', authCtrl.register)

router.post('/login', authCtrl.login)

router.post('/logout', authCtrl.logout)

router.post('/refresh_token', authCtrl.generateAccessToken)


module.exports = router

authCntrl code

const Users = require('../models/userModel')
const bcrypt = require('bcrypt')
const jwt = require('jsonwebtoken')

const authCtrl = {
     register: async (req,res) => {
         try {
            const { fullname, username, email, password, gender } = req.body
        console.log(req.body);
        res.json({msg: 'registered'})
     } catch (err) {
        return res.status(500).json({msg: err.message})
     }
 },
 login: async (req,res) => {
    try {
       
    } catch (err) {
       return res.status(500).json({msg: err.message})
    }
},
logout: async (req,res) => {
    try {
       
    } catch (err) {
       return res.status(500).json({msg: err.message})
    }
},
generateAccessToken: async (req,res) => {
    try {
       
    } catch (err) {
       return res.status(500).json({msg: err.message})
    }
}
}

 module.exports = authCtrl

auth router code

const router = require('express').Router()
const authCtrl = require('../controllers/authCtrl')

router.post('/register', authCtrl.register)

router.post('/login', authCtrl.login)

router.post('/logout', authCtrl.logout)

router.post('/refresh_token', authCtrl.generateAccessToken)


module.exports = router

package.json

{
  "name": "web",
  "version": "1.0.0",
  "description": "",
  "main": "server.js",
  "scripts": {
    "dev": "nodemon server.js"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "bcrypt": "^5.0.0",
    "cookie-parser": "^1.4.5",
    "cors": "^2.8.5",
    "dotenv": "^8.2.0",
    "express": "^4.17.1",
    "jsonwebtoken": "^8.5.1",
    "mongoose": "^5.11.13"
  },
  "devDependencies": {
    "nodemon": "^2.0.7"
  }
}

the thing is that everything seems like its okay but when i open localhost in the browser it doest show
and in postman too
in the terminal it says

server up and running 5000
Connected to mongodb

could be that the dependencies that im using are a bit outdated but im trying to follow a tutorial that was made in January of this year, so i dont want to change the dependencies or update them.