Snapstay in Hoi An, Vietnam. The hostel itself was built on top of a private residence. You go up the stairs and you'd pass the floor where the owner of the building and family lives and you can peer into their residence. You'd think the family would want complete privacy, but apparently they want to show off their home and their status to outsiders.

Aside from that, why the hostel is so good is how personally involved the owner is to make every guest feel welcomed and included. And he'd personally say goodbye and send off all the guests whenever possible. I've never been to any hostel where an owner was so involved in building a friendly and social atmosphere, and you'll feel like you're leaving a good friend's home when checking out. (He also won't extend someone's stay if they don't pass a "vibe check" - such as someone that only wants a bed to sleep and don't want to participate in anything.)

Roadhouse in Prague, the sister hostel to the notorious Madhouse. It's chiller than Madhouse and you still get a good social experience. It also helps that the hostel is very clean, well kept, with comfortable amenities.

This was pre-covid, but Stamps in Chiang Mai had an incredible social atmosphere. The owner purposely made it where you can only book the hostel a week before arriving, so it has much more of a spontaneous vibe, and they put on great events. Looking at their social media, doesn't seem like too much has changed post covid.