Knock knock / Who’s there? / Yah!

Knock knock
Who’s there?
Yah!
Yah who?
Naaah, bro, I prefer google.

This joke is a knock-knock joke. The critical element of this joke is the pun centered around the phrase "Yah who", which sounds like "Yahoo", which is an internet search engine. The jokester intentionally misunderstands the listener's response to be a query asking the jokester if they use yahoo.