First off, this json formatter was made by @vbodurov and he is still hosting it on his personal website as he has been doing for years. I consider it to be the "best" in-browser json formatter.
He made the code available via Codeplex and also commented that the code is of course also available via the ol' "view source" method. :)
I asked @vbodurov if I could import the project to Github and he said yes. Why should I bother to import this to Github? Because, I saw someone else on Github describe an inferior json formatter as "the best". :)
- pretty printing
- syntax coloring
- interactive folding
- dynamic folding
- copy/paste of output works well
- permlink feature (all state saved in GET url)
- interactive configuration
- easily adapted for use inside other projects
Have a look at the issues list.