Who is viewing a thread

[mattywatson]

Hi, I was wondering if the feature which allows you to see users currently viewing a thread, like the image below, is a vB option or an add-on?

https://vborg.vbsupport.ru/

Like at the bottom of this page:

Currently Active Users Viewing This Thread: 1 (1 members and 0 guests)
mattywatson

Edit: I found it.