A good hostel and location - convenient interchange to the metro and the pier. I've stayed there 2 times already.
It makes sense to pay a little extra for a 4-bed room.
The Klass hostel is probably one of the best I've been to. The staff is very friendly, always open to dialogue. The rooms are clean and well designed. There is a terrace on the top floor with a view of the whole of Istanbul. It is located in the very center, the metro is visible from the window, it is very easy to get to any tourist points. I advise you!
A pretty good hostel. Nice beds. Clean and tidy. The guys managers are great, they speak English profusely. The price per day is about 9 euros.. But it is cheaper to book via e-mail.