I saw something on YouTube and it looked cdazyyyy Diablo

illegal to discuss here, sorry

no its not lol, this is a mods forum

What is it guys why is it like Diablo is it single player?

Might be thinking of MedianXL

incorrect, illegal to discuss mods here

Is that it also like project Diablo I think?

Wtf is it?!?!?! Why does it look so different it is single player?

Median XL is a complete overhaul - new skills, revamped itemization, custom endgame content.

Single player supported and the single player has buffed item drop rate to compensate.

How do I play .

Do people play on battle net?

No. Install diablo 2 as regular. After at the home page (https://www.median-xl.com/), you should see a big ass red button which will give you the setup.
Use the setup, it will do everything for you. You will get a new launcher for the mod and from there just hit play. Its up to you if you want single player or online. Even with single player, people try to trade items through some stuff but I dont do it personally so I know nothing of it.

If you plan to follow any guide, make sure any guide by chucknorris is ignored, he's a complete retard.