How to know which website is built on which language

Answer 1

https://security.stackexchange.com/questions/117131/how-to-find-out-what-programming-language-a-website-is-built-in
web application - How to find out what programming language a ...

Answer 2

btw you can audit any website and get many helpful answers too,
open the website you wanna audit on chrome
then press F12
then audit option in the end.

Answer 3

I do it with chrome Dev tools and analyze elements , sources, network Http requests, requests , animation etc , but ☝ stackoverflow link was good too , good one Nithiwat