Which building is the most higher?

The tallest building in the world, as of my knowledge cutoff of September 2021, is the Burj Khalifa, located in Dubai, United Arab Emirates. The Burj Khalifa stands at a height of 828 meters (2,716 feet) and has 163 floors above ground. It was completed in 2010 and has held the title of the world's tallest building since its construction.

However, there are always new skyscrapers and buildings being constructed around the world, so it's possible that another building may surpass the height of the Burj Khalifa in the future.