The Get Users endpoint returns the view count of a channel. Subtract the value at the start of the stream from the value at the end of the stream and you have the total views from that stream.
Keep in mind that this is the number of VIEWS, not the number of viewers which is not a metric 3rd party developers have access to.
Also worth noting that those stats sites often misrepresent data, for example that image shows a “viewers attendance” stat, which they’ve simply calculated by dividing the total live views (426795) by the stream duration(~3.77 hours), except that this is just average views per hour, and is not viewer attendance as it’s possible for a viewer to be counted as more than one view, and also possible for a viewer not to be counted as a view. Sites like TwitchTracker pretend to know more than they actually do, and aren’t genuine about what they provide in an attempt to get more users.
“The Get Users endpoint returns the view count of a channel. Subtract the value at the start of the stream from the value at the end of the stream and you have the total views from that stream.”
But this number is not exact either because there may also be views of other videos on the channel during the period of time covered by the stream, right?
Twitch doesn’t disclose what specifically counts as a view, to prevent people gaming the system. There will always be a margin of inaccuracy in any 3rd party analytics service.