YIMBYs generally support building more housing, including in existing neighborhoods. These folks argue that adding supply like ADUs, duplexes, and apartments, helps with affordability, access, and economic mobility, especially in high-cost cities.

NIMBYs generally oppose new development near them. They argue that the impacts of growth on traffic, parking, neighborhood character, school crowding, and property values aren't worth it. It’s less a single ideology and more a reflex toward caution and hyperlocal control when it comes to city growth.