Expressjs 503 service unavilable

I have an app running on express.js. Everything was working so far, all the API calls to the backend are successful but it stating throwing the below error.

Access to fetch at “URL” from origin ‘http://localhost:3000’ has been blocked by CORS policy: No ‘Access-Control-Allow-Origin’ header is present on the requested resource. If an opaque response serves your needs, set the request’s mode to ‘no-cors’ to fetch the resource with CORS disabled.

GET request URL net::ERR_FAILED 503 (Service Unavailable),
I see the above errors whenever I switch tabs inside the app.

I restarted the server and redeployed the code, but of no use.
Any suggestions on what needs to be done?

Hi there,

CORS errors aren’t usually related to anything Render is doing. Online research will be your best resource here, e.g.

Let us know if you have any further questions.


Render Support Engineer, MT (UTC-6, UTC-7 in Winter)

i’d like to point you to this i just posted.

cors errors im getting seem to be due to cloudfare afaik