What is the significance of the _sm_nck=1 querystring?

Question

What is the significance of the querystring:

_sm_nck=1

that I see appended to a lot of page requests? What adds it and why?

We are seeing the occasional page request coming into our site with that parameter added, usually as a second request for the same page from the same IP address a few seconds later. Also if I 'Google' that parameter I see a high number of search results have it appended too.

Answer 1

I think it has something to do with ZScaler not having the site in its database of sites. See the image below. I did not add the _sm_nck myself.