javascript – CORS error on same domain?-ThrowExceptions

Exception or error:

I’m running into a weird CORS issue right now.

Here’s the error message:

XMLHttpRequest cannot load http://localhost:8666/routeREST/select?q=[...] 
Origin http://localhost:8080 is not allowed by Access-Control-Allow-Origin

Two servers:

  • localhost:8666/routeREST/ : this is a simple Python Bottle server.
  • localhost:8080/ : Python simpleHTTPserver where I run y Javascript application. This app is executing Ajax requests on the server above.

Any thought on what could be the problem?


And… the port was the problem. Thanks for your answers 🙂

If anyone is using a Python bottle server as well, you can follow the answer given on this post to solve the CORS issue:
Bottle Py: Enabling CORS for jQuery AJAX requests

How to solve:

It is only considered to be the same if the protocol, host and port is the same: Same Origin Policy

If you want to enable it you must follow Cross-Origin Resource Sharing (cors) by adding headers. Mozilla has examples

You need to add Access-Control-Allow-Origin as a header in your response. To allow everyone (you should probably NOT do that):

Access-Control-Allow-Origin: *

If you need to support multiple origins (for example both and, set the Access-Control-Allow-Origin in your reply to the value of the Origin-header from the request (after you verified that the Origin is white-listed.)

Also note that some requests send a preflight-request, with an OPTION-method, so if you write your own code you must handle those requests too. See Mozilla for examples.


The port numbers are different.

A request is considered cross-domain if any of the scheme, hostname, or port do not match.

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