I am using the fetch-API to send a GET request to a Spring Boot backend. The request looks somewhat like this:

  const response = await fetch(url);
  if (response.status === 200) {
      // do something
  } else {
      response.json().then(response => console.log(response));
  }

In case that I send a valid request, i.e. the url passed into fetch() is valid, everything works fine. In case that I pass an invalid url into fetch(), however, two things appear to be happenning:

1. A serer response message is thrown:

2. My Spring Boot backend return a ResponseEntity with a custom error message as body. This error message is logged inside the else-block of the above code snippet:

While I do expect the second point to be happenning, I cannot explain the first. I don't understand why this server-response error is logged into my browser console. I do have a few catch-blocks inside my code, something like:

const response = await fetch(url).catch(error => console.log(error));

As far as I know, however, fetch only throws an error if a network connection error occurred or similar. A response code not equal to 200 does not result in fetch throwing an error. So, as I said, I don't know where this error message comes from and I was hoping that somebody does, maybe it is something generic to the fetch API that I just don't know?