JSONCompare, the advanced version of the legendary JSONLint validator, is a fully featured JSON tool that allows you to directly input and validate JSON code, upload and validate multiple (batch) JSON files simultaneously, and also compare (diff) and merge two JSON objects.
And if you're looking for distraction-free mode, simply click the 'Fullscreen Editor.'
Credits & Source
Built and maintained by CircleCell. You can grab the JSONCompare.com source code from GitHub here.