Github repository:
https://github.com/hobbie71/MakeCode-Arcade-Sprite-Generator

Project ID:
3a021bd1-db69-4e85-9cdc-24f00ad39bde

Hey!

So I have a react frontend. just a static site that's working.

And I have a FastAPI backend.

Every time I go to my frontend URL, go through my app, and do something that calls an API from my backend, I get this error:

...has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource.

To debug this, I went ahead and added this to my ENV variables

CORS_ORIGINS="["*"]"

and somehow, I still get this errors. I'm assuming it's something wrong with my backend code? When I run this in a dev envornment, it works fine even when adding specific urls like this:

CORS_ORIGINS="["http://localhost:3000", "http://localhost:5173"]"

So, I'm not sure why I'm getting this error. I would appreciate any help.

Even debugging tips or possible causes of the issue would be a huge help.

I've been at this for too many hours, so I'm going to go to bed.

Thank you for reading this post and taking the time to help me find a solution.