CORS issue referencing an externally hosted schema using API Designer


I am getting this error from API Designer when I try and reference an externally hosted schema:

error: cannot fetch, check that the server is up and that CORS is enabled(HTTP 400)

The error appears as a red cross in the editor.

My RAML file looks like this:

#%RAML 0.8
title: requisitions
version: v1

I’ve checked my CORS configuration on my hosted schema and it all seems OK.

I’ve also used a third party site that does CORS testing and it says that CORS is OK for a GET request.

Any idea what this could be?


Hi @abraae,

I’m seeing the same thing in API designer for the schema you shared, but I hit that endpoint with both Postman and curl to take a look and it seems the Access-Control-Allow-Origin header isn’t being returned by the server. Might be worth double checking your CORS configuration.



Wow, thanks for that. I was getting fooled by our office squid proxy as I tried different combinations. Sorry for the confusion.

I’ve fixed my CORS configuration (I believe) and the headers are now definitely appearing when I test with curl (thanks for the tip on that btw).

But API designer still throws the same error.

Any more help appreciated!


Hmm, It’s working for me now - just imported that schema into API designer and it was fine.

#%RAML 0.8
title: someAPI
  - requsition: !include

Inspected the network traffic, and the call is executing fine and the JSON is getting fetched. Maybe try clearing your cache?

Sorry I can’t be more help!


I’ve cleared caches, tried 3 different browsers, two OSs and different network connections, and still I get just the same error. I can’t understand why it would work for you but not me. Really annoying since otherwise API designer looks good for our needs. I’d appreciate knowing your configuration, e.g. browser + os + machine if at all possible.

Thanks for your help anyway, much appreciated.


I’m on OSX 10.7.5 on a MBA, using Chrome Version 36.0.1985.125. I’m using the hosted API Designer at

Where do you have the API Designer running? Is it your own local version, hosted somewhere, etc?


Aha! I tried to use that portal but new accounts are no longer allowed there. I was directed to instead use:


Works for me there, too >_<.

Might be worth opening an issue over on the API Designer github so the core contributors from MuleSoft could look into why it’s working for some folks and not others?


Will do, many thanks.