How to set variable scope to the browser in asp.net core web api?

Hi

I want to create variable and make its scope to the browser so every user enter my asp.net core web api through his own browser sets the variable as he needs. i tried to use the static variable but it lives in the scope of the program lifetime and when user sets the variable and other user sets the same variable the previous user sees the value of the variable being set by the other user which is big problem i want every user sets the variable for his own and the variable being reset as he leave the website or close the browser tap or the browser itself.

Iam using asp.net core web api 3.1