Thus so far, Hyper Sonic's only appearance is in Sonic the Hedgehog 3 & Knuckles. In the game, Hyper Sonic looks very similar to Super Sonic, sharing the same body proportions and upturned head spikes. However, Hyper Sonic flashes in all seven colors of the Chaos/Super Emeralds and has large flashing sparks (similar to the Invincibility item) floating around him. Also, when moving, he leaves several after-images.
Hyper Sonic has all of Super Sonic's abilities, such as invincibility to all attacks, improved speed and strength and greater jumping abilities. Since Hyper Sonic is generally an upgraded version of Super Sonic, it can be assumed that all of Hyper Sonic's physical abilities surpass that of Super Sonic, meaning he possesses greater strength and speed. Hyper Sonic also has some new and improved abilities from Super Sonic, such as the ability to breathe underwater, further increased speed, is fully invincible towards any attack or environment, and an unnamed mid-air dash attack that can be performed in all directions, which destroys all enemies onscreen, excluding bosses, which is referred to by some fans as "Sonic Boom" or "Hyper Flash". This is Sonic's most powerful form to date.
As with all Chaos Emerald/Super Emerald-caused transformations, once Hyper Sonic runs out of Rings, his transformation will end and will revert back to normal.
Hyper Sonic's name comes from the term hypersonic, which is a speed above supersonic (which is defined as any speed Mach 5 or greater than it).
Hyper Sonic's double jump ability can somehow force him to enter a Bonus Stage without jumping into the ring of stars.
In Launch Base Zone Act 2, if Sonic transforms into either Super or Hyper Sonic underwater, then he will have a color scheme similar to that of Shadow the Hedgehog for one of the frames of his transformation.
Like Tails and Knuckles, if you turn into Hyper Sonic with S in Debug Mode when the level ends, and quickly turn back into a box, the word Sonic in "Sonic Got Through Act 1/2" turns into Hyper Sonic's colors.