Dwell Time
IntermediateDwell time is how long a user stays on a page after clicking a search result, measured until they return to the results page.
Only the search engine can observe this number, because both ends of it, the click on the result and the return to the results page, happen outside the site; neither search-engine reporting nor a site analytics tool publishes it. In everyday SEO conversation the term is often used in place of time on page, although they are different things, and that ambiguity is the root of most confusion around it. Google has not confirmed dwell time as a direct ranking signal, so treating it as a ranking lever is an assumption rather than a documented fact.
How it is calculated
Dwell time = time of return to the results page minus time of the click on the result
The result is in seconds. The calculation is only possible on the search engine's side; if the user never returns to the results and closes the browser instead, there is no return to record and dwell time stays undefined.