Urban cohousing, like all urban housing, is densely packed but still contains all the core features of cohousing.
In urban communities, units are more likely to be stacked to 3 or 4 stories. The common house is probably a first floor space below other units rather than a free-standing building. The shared outdoor space is likely to be a common courtyard rather than a playground or lawn. Parking may be reduced or limited to street parking if the community is close to public transportation options.
Urban cohousers tend to be within walking distance of restaurants and grocery stores. They often have some of the smallest cohousing units, which if anything encourages them to make more use of their common areas and interact with each other even more.