JSON - Online linter
Exactly like my SQL - Formatting tool, it's always useful to have a tool in your favourites that lets you copy/paste a JSON character string and display it as a tree-view with or without code folding feature.
I use it quite regularly when I'm writing a JSON string and I want to check that there are no syntax errors (lint) or, on the other hand, and for example, when I call an API that returns JSON and I want to analyse the code received. In these cases, the collapse functionality comes in very handy.