json and simplejson are the same modules. It's just that json is based on an older version of simplejson, since the latter is not tied to the Python release cycles, and updates faster.

Simplejson also works with older pythons that didn't have json built-in (2.4 etc).

People using it is not about needing a JSON because there isn't one in the standard library, it's because it was faster than it. 2 times faster loading, and somewhat faster dumping (depending on json and simplejson version).

>* Also surprised to see Django having 10m more downloads than Flask.*

Django is much older and more established. When Flask was still a new thing, Django had several versions out and people using it.