Failed to register a ServiceWorker for scope ('http://localhost:3000/') with script ('http://localhost:3000/mockServiceWorker.js'): The script has an unsupported MIME type ('text/html')

[f1nl0wt3ch]

Hello!

After many tries, I could not figure out what the issue I am facing with. After configuring with MSW, it works perfectly in the first try. But after that, when I try to start MSW again for testing, I get the following issue:

Failed to register a ServiceWorker for scope ('http://localhost:3000/') with script ('http://localhost:3000/mockServiceWorker.js'): The script has an unsupported MIME type ('text/html')

I do many things to try to solve this issue, but it didn't help

1. Delete mockServiceWorker.js from public folder and try to generate it again using npx msw init public/ --save-dev
2. Uninstall and install MSW
3. Remove node_modules, package-json.lock and install all dependencies again

Could you please help me?

[kettanaito]

Hi, @f1nl0wt3ch.

It appears that something in your app stops serving /mockServiceWorker.js at some point. text/html MIME type means that now there's a 404 page under that resource instead of the worker script.

You have to investigate your app's setup and fix that. There's nothing we can/should do on the library side.

[f1nl0wt3ch]

It seems to cause from the handlers. I tried with another lower version (2.7.5) and it's back to work again. Thank a lot for your answer! What's amazing and powerful testing library!