This article contains a list of glitches from Sonic the Hedgehog (1991). Unless otherwise noted, all glitch names are conjectural. Many of them have not been confirmed by Sega.
List of glitches
- Missing "Press Start"
The text "Press Start" was supposed to show up in the final game, but does not. It was soon discovered that the text does still exist in game, but is not shown due to a programming error. The "Sonic Team Presents" screen uses the same chunk of memory as the "Press Start" button and as the memory is not cleared right, "Press Start" will not appear. It's possible that the "Sonic Team Presents" screen was added or modified after the title screen was finished and the game's code was not updated to accommodate the change.
- Spike Hit Bug:
When Sonic is hurt, his temporary invincibility frames will not protect him from spikes. The most common case of this glitch occurs in Green Hill Zone, where two sets of spikes are next to each other. Sonic will bounce from one set to the next and die instantly. Even with a shield, Sonic will just bounce back and forth until he dies on the third hit. This glitch also applies to other attacks. If hit by a Badnik, Sonic can die if he touches spikes directly after. This glitch was fixed in the REV 01 version (only in Japan) in Sonic Jam if Spin Dash is enabled in the bonus unlockable version of Sonic the Hedgehog in Sonic Mega Collection (which was the default version in Sonic Mega Collection Plus), and in the 2013 mobile re-release (also only if the Spin Dash is enabled).
- Game crash in Labyrinth Zone:
If the player uses the spin attack past the goal post on the right side of the screen, then presses the down button in Labyrinth Zone Act 1 or 2, the game will crash with an illegal instruction message. This glitch is much less likely to occur in the European version due to the game's overall slower speed.
- Marble Zone unsolid block glitch:
Some of the blocks in Marble Zone Act 2 and 3 allow the player to crouch through them; however, the player will die if they attempt to stand up while crouching in the blocks.
- Final Zone glitch:
If the player hits Dr. Robotnik two times on the last hit, they will have to hit him another 255 times to defeat him, which is not possible under the time limit.
- Background glitch:
In any Zone, the player must first enter the Debug menu and kill themselves. Right before the player falls out of the screen, they must become an item, take themselves back to the top, then place themselves down, which will cause the screen to glitch. This also works with Sonic the Hedgehog 2, Sonic the Hedgehog 3, and all lock-ons of Sonic & Knuckles.
- Sonic Dies by Going Too Fast:
In rare cases when Sonic goes through the two shuttle loops, he may die after exiting the second shuttle (before the section with several rings in the air). This is because the game registers Sonic flying out of camera view as him falling into a bottomless pit.
- Walk around the Signpost area:
After the player goes past the signpost at the end of the level, if they go past the screen to the right and jump just as the signpost stops, it will then be possible to walk around in the signpost area. This glitch can also be used in Sonic the Hedgehog 2.
- Outrunning the screen in Green Hill Zone:
In the 8-bit version of the game, in Green Hill Zone Act I, there is a hill with an invincibility upgrade on top and speed shoes after it. The player must get the speed shoes and go left back up the hill. Once on top of it, they should run to the right and roll down the hill. Sonic will be thrown upwards and out of the screen, and the camera will start moving to the right until it stops at the goal post (where Sonic will be standing). The player must then move to the left and touch the goal post to finish the level, skipping most of it.
- Tails glitch:
In the iOS and Android version of the game, the player must select No Save Mode and then enable Debug Mode. From there, they should select character 00, go to Green Hill Zone Act 3, then kill themselves twice with spikes. Once that is complete, they must kill themselves once more by using Debug Mode to go under the ground and then deactivating it, causing them to receive a game over. Finally, they need to start a Sonic only game, and they will now have Tails. (Note: If the player beats the act, Tails will remain permanently)
- Golden Sonic glitch:
In the iOS and Android version of the game with Debug Mode activated, the player must place down an S monitor, smash it, and enter Debug Mode again. After the player hears the transformation noise, they should exit Debug Mode. Sonic's fur will turn golden, but his quills will not be upturned, and he will run normally rather than flying.
- Sonic's Super design:
In the iOS and Android version of the game, the player must play as Sonic and turn Super in any way with Debug Mode enabled. They then need to activate Debug Mode, pass the Goal Post and wait for the sign to stop spinning. The player should not be able to move, but if they press back athey the player will be able to move again. When the zone's music starts again, the player must exit out of Debug Mode. Sonic will mostly still be Super Sonic, but his speed will return to normal and his fur will return to its regular blue color. Sonic will remain in this state until the player either reaches the next act, or ends the game.
- Final Scene crash:
If the player beats the final zone with Debug Mode active, then changes into an item during the scene with Sonic running in Green Hill Zone, they'll be able to control Sonic. They should travel to the right side of the level, jump on the platform that is slightly beyond the screen, then jump again. Sonic will "die" (the death sound will play), and the game will show a blank white screen before crashing.
- Water jump glitch:
In the iOS and Android version of the game, if the player goes to any act in Labyrinth Zone and then travels to a location where they can stand half in and half out of the water, they should wait for the water to be at the character's waist and jump. The character will jump as high as a red spring would launch them. This glitch also works in the Sonic the Hedgehog 2 remake, although it is more difficult to perform there.