Monitors (referred to in Sonic Adventure and Sonic Adventure 2 as Item Boxes) are staple objects in the Sonic the Hedgehog games. These breakable objects appear as small boxes resembling computer monitors/televisions, or bubbles, depending on the game's time. If the player breaks them open, they will receive a power-up or bonus, with a few exceptions.
Monitors (like most badniks) can be broken from directly above or from the sides, assuming that the character is performing either the jumping or rolling spin attack. When one is suspended in the air (e.g. hidden in a tree in Green Hill Zone) or stuck to the ceiling), striking it from below causes it to fall to the ground. When playing as Knuckles, they can also be broken by gliding into them.
The Advance series, and some 3D games have these powerups inside capsule-like objects. These can be broken by touching them, with the exception of Sonic Advance.
Monitors in more recent games (Besides Sonic 4 and the Classic gameplay of Sonic Generations) have become non-existent, with the last major 3D title to have any being Sonic 06, in which they were removed entirely by the final game. Sonic Unleashed and Sonic Colors removed Monitors entirely, with the only remnants of any sort of monitor being the 1-Up Life icon, which is no longer in a monitor, and can be picked up like a ring. There are now slightly larger rings, which act as a Super Ring monitor. Speed Shoes are no longer needed, as Sonic can run as fast as them with the Sonic Boost. Invincibility and shields are also no longer needed, as the Sonic Boost acts as a ram-able shield, eliminating the need for either.
In early Sonic games, monitors were modelled off real computer monitors. Sonic the Hedgehog 3 and Sonic & Knuckles use monitors based on the Macintosh Color Classic, released by Apple in early 1993.
- Super ring gives the player 10 rings in all games except the Advance and Adventure series, where the number of rings is specified (5, 10, 20 or 40) or randomised (1, 5, 10, 20 or 40).
- Power Sneakers increase the character's speed temporarily.
- Shield monitors grant the player a shield (available in various types since Sonic the Hedgehog 3) that protect them against one hit from an enemy or hazard.
- Invincibility monitors grant the player temporary invincibility.
- Extra life gives the player an extra life (1-up). The icon is usually the face of the character being played as. In Sonic the Hedgehog 2 (16-bit)'s two-player competition mode, Sonic and Tails have their own monitors that give them an extra life, regardless of who broke it. The game's scrapped Hidden Palace Zone features a Tails monitor, which functions like a normal 1-up monitor regardless of the character being played as.
- Dr. Eggman monitors cause one hit of damage to the player character. This is the only type of monitor that harms rather than rewards. It debuted in Sonic 2, although graphics for it existed in Sonic 1.
- Teleport (Sonic the Hedgehog 2 (16-bit)) - switches Sonic and Tails' positions in competition mode and debug mode
- Switch (Knuckles' Chaotix) - switches the characters' positions for a certain amount of time
- Combine Ring (Knuckles' Chaotix) (Sonic Mania) - protects your rings so if the first player is hit, he only loses one ring. He has a few seconds to get that ring, otherwise it breaks into all the lost rings. Getting the single ring recovers all your lost rings. It is notable that a similar monitor exists in Sonic CD but has no use.
- Big and Small (Knuckles' Chaotix) - resizes the character who breaks the monitor for a certain amount of time. Small characters have a limited range of motion, while big characters cannot be held.
- Change Character (Knuckles' Chaotix) - This monitor cycles between faces of possible characters. When broken, the second player becomes whoever was pictured at the time for a certain amount of time.
- Emerald (Sonic Triple Trouble): transports the player to a special stage.
- Stopwatch (Sonic Chaos and Sonic Triple Trouble): In Sonic Chaos this stops the special stage timer for a few seconds. In Sonic Triple Trouble it resets the special stage timer.
- Pogo (Sonic Chaos and Sonic Triple Trouble) gives the player a small spring that sticks to their feet.
- Rocket shoes (Sonic Chaos and Sonic Triple Trouble) allow Sonic to fly around temporarily.
- Snowboard (Sonic Triple Trouble) monitors grant Sonic a snowboard that he can ride.
- Skateboard (Sonic Generations) monitors appear in Classic City Escape, allowing Sonic to ride around loops and use Jump Pads to reach higher portions of the level.
- Blank ("Sonic the Hedgehog 1 (16-bit)") a monitor available only in that game's debug mode and it does nothing.
- "S" (Sonic the Hedgehog (16-bit)) ("Sonic CD") (Sonic the Hedgehog 3) monitors are only available in that game's debug mode. They grant the character 50 rings and instantly transform them into their super form, irrespective of how many emeralds they have. The "S" monitor was also hidden in Sonic 1, and was only viewable via hacking; it did nothing. It exists in Sonic CD, also in debug mode only, where it acts as a combination of Speed Shoes, invincibility, and a shield.
- Goggles (Sonic the Hedgehog 1 (16-bit)) probably protected Sonic from drowning in the same way as a water shield does in Sonic the Hedgehog 3 and later games. Their functionality was not programmed in the finished game; they can only be implemented through hacking and do nothing. (In the iOS/Android remake, it can be placed in debug mode, where it acts as a shield, but only underwater. It does not, as commonly believed, affect Sonic's ability to hold his breath.)
- Pogo (Sonic the Hedgehog 2 (16-bit)) possibly going to have the same affects as the one from Sonic Triple Trouble; only viewable through hacking and does nothing when broken.
- Stopwatch (Sonic CD) can be placed using debug mode, but has no effect other than to freezing certain level elements (animation, etc.)
- The Item boxes appearance has changed with the times. Sonic 1, 2, and CD all had CRT Monitors for their boxes. Sonic 3 had monitors resembling Apple computers from around that time. Sonic 4 has them resemble modern flat-panel LCD TVs, while Sonic Generations kept the retro CRT look updated for HD.