angular-cli/docs/documentation/stories/proxy.md

Proxy To Backend

Using the proxying support in webpack's dev server we can highjack certain urls and send them to a backend server. We do this by passing a file to --proxy-config

Say we have a server running on http://localhost:3000/api and we want all calls to http://localhost:4200/api to go to that server.

We create a file next to projects package.json called proxy.conf.json with the content

{
  "/api": {
    "target": "http://localhost:3000",
    "secure": false
  }
}

You can read more about what options are available here webpack-dev-server proxy settings

and then we edit the package.json file's start script to be

"start": "ng serve --proxy-config proxy.conf.json",

now run it with npm start