1) Create a folder on Desktop or Any other place ex. users-api-server 2) Open Terminal and Go to the folder directory . ex. cd /Users/apple/Desktop/users-api-server 3) Init npm . " npm init -y " 4) Install JSON-SERVER. "npm i -g json-server" 5) Create "package.json" file into folder. ex users-api-server/package.json { "name": "users-api-server", "version": "1.0.0", "description": "", "main": "index.js", "scripts": { "test": "echo \"Error: no test specified\" && exit 1" “json:server”:”json-server — watch db.json” }, "keywords": [], "author": "", "license": "ISC", "dependencies": { "json-server": "^0.16.3" } } 6) Create "users.json" file into flder. ex users-api-server/users.json { "users": [ { "id": 1, "first_name": "Robert", "last_name": "Schwartz", "email": "rob23@gmail.com" }, { "id": 2, "first_name": "Lucy", "last_name": "Ballmer", "email": "lucyb56@gmail.com" }, { "id": 3, "first_name": "Anna", "last_name": "Smith", "email": "annasmith23@gmail.com" }, { "id": 4, "first_name": "Robert", "last_name": "Brown", "email": "bobbrown432@yahoo.com" }, { "id": 5, "first_name": "Roger", "last_name": "Bacon", "email": "rogerbacon12@yahoo.com" } ] } users-api-server folder should be look like following way 7) Then start server. Go to the users-api-server folder on terminAL ex. cd /Users/apple/Desktop/users-api-server The "json-server --watch users.json ". Then mock api server will start output like below Demo through POSTMAN Demo through IDE ( IntelliJ ) If you are not start json server and try to execute api . Then you will get following error