I try to communicate with a service which accepts http requests but replies with strings (in particular no http-headers). In Firefox the response upon a GET-request is displayed as
while in Edge it will produce the error
Is there a way to accept such invalid http responses with the http client get.vi?
I would not try to rely on this working on any browser. Trying to do HTTP when the protocol isn't actually HTTP should cause an error and for a change it sounds like Firefox doesn't implement proper error handling and validation which would be a security risk.
What you'd need in this case is to write some other software that runs as a server to service requests from the web app, make requests to the 3rd party service but get the data back expecting it to not be properly formatted as HTTP, and return the response as properly formatted HTTP. This could be done with LabVIEW Web Services to handle the requests from the web app, or any other environment where you can do TCP communications.
Wait, you posted this in hobbyist forums but it sounds like you're asking about a G Web app?