512K Day, sometimes called the "Internet Slowdown," is a day when people who own websites and use the internet "slow down" their websites to show support for net neutrality. Net neutrality is a principle that requires internet service providers (ISPs) to treat everyone equally who uses their service, no matter which website you visit. On 512K Day, people who own websites put a warning, or what looks like a loading bar, on their website to show their support for net neutrality.