The script has an unsupported MIME type ('text/html')

[bodadotsh]

Hi I've written a small project with create-react-app, it runs in the browser 'http://localhost:3000/' with 'npm start' but i'm seeing these two errors in the console:

The script has an unsupported MIME type ('text/html').  :3000/service-worker.js:1
GET http://localhost:3000/service-worker.js net::ERR_INSECURE_RESPONSE  :3000/service-worker.js:1

this is my package.json

{
  "name": "my-app",
  "version": "0.1.0",
  "private": true,
  "devDependencies": {
    "react-scripts": "0.4.1"
  },
  "dependencies": {
    "react": "^15.3.1",
    "react-dom": "^15.3.1",
    "react-redux": "^4.4.5",
    "redux": "^3.6.0"
  },
  "scripts": {
    "start": "react-scripts start",
    "build": "react-scripts build",
    "test": "react-scripts test --env=jsdom",
    "eject": "react-scripts eject"
  },
  "eslintConfig": {
    "extends": "./node_modules/react-scripts/config/eslint.js"
  },
  "standard": {
    "globals": [
      "describe",
      "context",
      "before",
      "beforeEach",
      "after",
      "afterEach",
      "it",
      "expect"
    ]
  }
}

[gaearon]

Can you please share your browser version and OS?

[bodadotsh]

browser version: Version 53.0.2785.116 (64-bit)
os: OS X El Capitan version 10.11.6

[gaearon]

Could you please show a screenshot? Thanks.

[bodadotsh]

just created a new project from scratch, still getting this error.

screenshot here:
http://i.imgur.com/EjywosK.png

did 'npm uninstall -g create-react-app' and reinstalled it globally, made a test app still same error.

[gaearon]

Interesting. Maybe some transitive dependency is doing something funny.
It’s not an error so you shouldn’t worry about it.
I’ll try to find what causes it when I’m back from vacation but feel free to jump in and investigate.

[bodadotsh]

finally found the solution after days of 'googling'

run npm run prepublish inside the webpack-dev-server global library installed folder (/Users/bodaz/.npm-packages/lib/node_modules), and that seems fixed everything, the browser is back to normal and no more error messages at localhost:3000

for the record, the webpack version i had installed globally is webpack 1.13.2
and this is the link where i got my solution from: webpack/webpack-dev-server#326

[gaearon]

Why would a global webpack-dev-server matter?
We don’t use the global version anywhere as far as I know.

[gaearon]

Closing as it’s not clear how to reproduce this, and original author has resolved the problem.

[dongjinahn]

i saw this message too. (chrome)
but the message wasn't reproduced during testing on safari and private mode chrome.
so it seems chrome's extension script error i installed.

[nikhildev]

I've been running in the same issue. The local version is webpack-dev-server@1.16.2. Im running Windows 10, Chrome 56.0.2906.0 dev (64-bit).

At this point I'm clueless on what to do.

[rob-yoti]

I got this issue after running npm run build on a new app, and moving the build folder to my express application which then served it.

It appears the helmet middleware was interfering with the client side caching, so if you have this issue on a node server, it may be worth checking this.

[soulcm]

yes, I got this issue too, when I build my app and run it in a server side render application in express, the chrome show those two errors

[n3tr]

Maybe I'm wrong, the error is about service worker has been register for localhost:3000.

Can you open Chrome Dev Tools -> Application -> Service Worker and see if you have a service worker has been registered? If yes click unregister and refresh the page again.