For the average user on a home broadband connection, 30 megabits per second is considered a fast Internet speed. For heavier users, there are Internet plans that allow more than 100 megabits per second.
Fiber optic cables provide the fastest Internet connections. Google Fiber and other similar companies have Internet plans that can give 1 gigabits-per-second download speeds. These plans are only available in certain cities, although more locations are continually added.
Scientists are experimenting with fiber optics that could enable potential download speeds of over 255 terabits per second, though these speeds are unlikely to reach consumer hands anytime soon.