Some hostels do have age limits and might give precedence to younger travellers, or exclude them (if they have a bar in the premises), but most hostels will welcome guests of all ages, and will even accommodate children and provide smaller beds and cribs on request.
People under 18 cannot stay in dorms, even if they are travelling with an adult, however normally there is no age restriction for the private rooms.
Some hostels will have a curfew, some won’t. It depends on the type of hostel, on the hostel management policy and on the location of the hostel (there’s not much use in being able to come to the hostel at three at night if the hostel is on the mountains!). Many hostels featured on HostelsCentralstate their curfew policy right in their description.
Some hostels might have a lockout period. This is usually around lunchtime or early in the afternoon, and is meant to let the hostel staff clean the premises, carry out the daily ordinary maintenance etc. It is not so common any longer, so check with the hostel’s staff if you want to be sure.
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