JSON response format error - red dot\bullet before response

I am sending an AJAX request expecting JSON response. However, the returned JSON is preceded with a red dot\bullet which is causing a parse error.

Here is a screenshot from Postman:

The dot is not shown on Raw or Preview display, only on Pretty.

In Chrome Dev Tools Network tab it appears under Response. Preview is shown normally as if the dot isn't there.

As mentioned in a comment before: In Chrome, red dots usually represent non-printable special unicode characters.

Please check your server side code to prevent outputting those characters

If your files are encoding with UTF-8, better to encode them with UTF-8 without BOM. This can be easily done through notepad++. The steps are as follows,

1. Open your files in notepad++.
2. Go to Encoding option on the file menu.
3. Then select the option "convert to UTF-8 without BOM".

This may resolve your problem.

You need to clear you object buffer on server side. I am using PHP as my server side language and I faced similar problem and the solution was cleaning my buffer using ob_clean();