What is Dark Launch?
It is a go-live strategy in which code implementing new features is released to a subset of the production environment but is not visibly, ...

https://www.interviewquestionspdf.com/2017/01/what-is-dark-launch.html
It is a go-live strategy in which code implementing new features is released to a subset of the production environment but is not visibly, or only partially, activated. The code is exercised, however, in a production setting without users being aware of it.