1. Notepad++

a. JSON-Viewer plugin: https://github.com/kapilratnani/JSON-Viewer/releases

b. Shortcuts: Ctrl+Alt+Shift+M

2. Atom
a. File>Settings>Packages, search json>Language-json enabled;
b. Ctrl+Shift+v hot key to format json file;

3. Online json format tool:
http://json.parser.online.fr/