Vanity height is defined by the Council on Tall Buildings and Urban Habitat (CTBUH) as the height difference between a skyscraper's pinnacle and the highest usable floor (usually observatory, office, restaurant, retail or hotel/residential).
The world's tallest building, Burj Khalifa, is officially 828 meters tall, but its highest usable floor is 585m above ground.
Without this vanity height, the Burj Khalifa would still be the tallest building in the world, but only exceeding the Shanghai Tower's highest usable floor by 2 meters.
[1][3] The next potentially tallest building, the Jeddah Tower, could be over 1,000 meters tall, but its highest floor is planned to be 630m above ground.
[4][5] The CTBUH requires a structure's vanity height to be under 50% to be defined as a "building."