Sonic And The Mystic Gems (previously known as Sonic 1 Harder Levels) is a hack made by Eduardo Knuckles and his team Harder Project of Sonic the Hedgehogon the Sega Mega Drive/Genesis. The hack adds to the game a lot of new features such as the three known main playable characters, a checkpoint monitor, customizable level music playlist, a sweet and clear save data select menu, difficulty selection, a unique music menu and some other additional menus and screens which gives to the game a completely new gameplay experience.

Sonic the Hedgehog Mega Blitz is a hack of Sonic the Hedgehog (16-bit) made by SSE. It is named "Sonic the Hedgehog Mega Blitz (Sonic Mega Blitz)" Due to the fact that the hack is a "blitzed out" version of the original game.

Sonic the Hedgehog Megamix (commonly shortened to Sonic Megamix) is a work-in-progress multiperson disassembly modification of the original Sonic the Hedgehog videogame for the Sega Mega Drive / Genesis, developed by Team Megamix and more recently moved to the Sega Mega-CD. The game features the ability to play as one of five different characters: Sonic the Hedgehog, Mighty the Armadillo, Shadow the Hedgehog, Miles "Tails" Prower, and Knuckles the Echidna. It is an extensive reworking of the original game, featuring new art, music, abilities, layouts, and other things.

Sonic the Hedgehog Plus (often called Sonic 1 Plus) is a hack of Sonic the Hedgehog by Hivebrain. The hack is basically the same as the original game, except with a number of extra features and bugfixes.

Sonic ReOne is a hack created by DeltaWooloo which takes Sonic back to where he originally started 29 years ago in South Island. This hack features new palettes that cycle through every act just from bright morning to dark evenings. Iconic features from classic Sonic games arrived in this hack (see the features below) Eggman pumped up his bosses to make it harder when you annoy him by hitting him. The level design is a mix between linear and platforming which is something you see in Sonic games, but be careful that you don't go too fast. Eggman placed badniks and springs to prevent you from going to the end. The music is catchy and fun to listen to and suits the mood of the zones.CREDITSLevel designs: DeltaWooloo with some help from Dj. Joker27Music composers: Dj. Joker27, RuthlesstheHooman, TheInvisibleSun and JoenickROS, LackofTrackPalette designers: DeltaWooloo, RuthlesstheHooman, maple_t and KCEXECoders: DeltaWoolooand RandomNameTitle Screen logo made by mePeople who helped me along the way: Iso Kilo, AUORA_FIELDS (Natsumi), MarkeyJester, Samey, ProjectFM, Tanman Tanner, Trickster, Inferno, RuthlesstheHooman, nineko, KCEXE and Dark LipsSpindash guide by Lightning, Puto, shobiz, MecuryShield attract and bug fixes from Mecury's ReadySonicPeelout and CD spindash by LuigiXHero and MecurySonic CD roll jump and slow ducking, title screen centering and fix Sonic 1 debug by Iso KiloFade to white routine and removing water surface object by ProjectFMAir roll by InfernoSonic 2 spring object, coconuts and stars by RandomNameCorrecting PAL music by CrashStarposts by ShooterSonic 3 and CD SFX: KCEXERoute 113 SMPS by ProjectFMSnake Man SMPS by ValleyBellSonic Heroes Special Stage 2 by S_T_DA few bug fixes and Nemesis and Kosinski decompression by vladikcomper

Sonic the Hedgehog Thrash is a ROM hack of Sonic the Hedgehog 2 by DalekSam, though it was originally a hack of Sonic 1. It also uses the Sonic 2 Clone Driver.You can also play as Knuckles, credit given to Spanner for the Knuckles object among other things. Honestly, I tried doing it myself but I failed, hard.As of August 2013, the project has since been rebooted from scratch.

Sonic The Hedgehog ZX (also known as Sonic 1 ZX or S1HZX for short) is a hack made by CarrascoZX0 and his team, Team ZX. This hack features the ability to play as Sonic the Hedgehog or Knuckles the Echidna. The hack also features new art, abilities, level layouts, music and much more!

Sonic the Hedgehog Extended Edition is a hack in progress by Cinossu of Sonic the Hedgehog on the Sega Mega Drive/Genesis. In this version of the game, instead of new or fully edited zones, all the original zones are kept intact with minor editing to the acts. Instead, this hack extends the game beyond its original capabilities, including a zone map with warp rings to each act (much like in Sonic Advance 3), saving via SRAM slots (like in Sonic the Hedgehog 3), obtainable upgrades such as the Spin Dash and Super PeelOut (like in the Megaman X series) as well as a new type of ring, emerald, and special stage to add to the mix.While work has not been shown on the hack for a while publicly, a lot of work goes on in private. This is mostly Cinossu either restarting the entire thing from scratch (currently on the 5th restart since conception), or constantly adding and refining new features and ideas. The latest restart is most likely the last one, however, as the disassembly is now so modular that the various chunks can be restarted rather than the entire hack.

Sonic the Hedgehog: Isle of Magnetic Artifacts is a sonic hack made By Neo Team Kyukyokuis a hack which aims to overhaul Sonic 1 using a Japanese-inspired aesthetic. The main feature of this demo is Blossom Gardens Zone, the resting area of the isolated, star-god worshipping Kuratranos tribe. BGZ is a fast-paced experience littered with swift-acting enemies, height-granting gimmicks, driving music, and advanced graphical effects. This new zone can be traversed with three playable characters: Sonic the Hedgehog, Miles "Tails" Prower, and Knuckles the Echidna. Sonic, in particular, features a set of unique sprites, the dropdash ability, and a new companion: Abbey the Flicky. Abbey can pick up nearby rings and circle potential targets for Sonic, including hidden monitors.Neo Team Kyukyoku MembersAngelKOR64: Character programmingChron D: Music arrangementDeltaWooloo: Level layouts, music arrangement, object ports, programming, sound effectsDaxKatter: Music arrangementDio-ZX: Character art, object artDrag109: Level artfuzzy: Level art, programmingiced t: Level art, object artInferno: Level layoutsInktitious: Level artJerry: Level layoutsKatKuriN: Level artKGL: Level layoutsKurk: Team Leader, level layouts, music arrangement, music compositionManiacShard: Object artNaotoNTP: Object artProjectFM: Creative direction, level art, music arrangement, music composition, programming, story planningRaendom: ProgrammingRivet: Programmingtwo^: Concept artyami: Level layouts, music compositionFormer MembersAmzroSevca: Concept art, story planningGemini0: Former team leader, general art, level layouts, programmingjrm1007: Concepts, object artHaz Rabbit: Concept art, programminglavagaming1: ProgrammingNotQuiteHere: Music arrangementpoly: Logo, music arrangementMr. Gandy: Character artXGSOAP: Character artPlaytestersAccelBladeOfChaosCertainly GlitchyCosmic EternityDaxKatterfengishGGK912Hooded EdgeKCEXEKNIJohnMattyMeara BlanchetteMCTravisYTProfessor RendererPXSleekflash-16Sr ParadoxosoapyyTheInvisibleSunUnusualSeekerResourcesAsuharaMoon: Wind-Up Koi spritesAURORA☆FIELDS: SMPS2ASM and AMPSCartoonsAnimate22: Tails and Knuckles spritesCuckyDev: GHZ ball baseflamewing - Ultra DMA Queue + optimized Kosinski (improved by vladikcomper and MarkeyJester) and Enigma decompression codeLone Devil: Metal Sonic spritesMainMemory: SonLVL and Drop Dash programming guideMarkeyJester: DualPCM and sound testMikel Nash: Sonic 3-style super sonic spritesObserver: Sprite ripsShibaMayo: ShibaSaturn spritessnkenjoi: Flex 2The Eighth Bit: Space Queens MIDITheOneMusaab: Sonic 2: The Alternative Spritestildearrow: FurnaceTeck: Super Mario Land - Ending Theme MIDIvladikcomper - optimized Nemesis decompression codeValleyBell: mid2smps, SMPS Converter, SMPS Research PackVladislavSavvateev: DMF2AMPSAssets From:Capcom no Quiz Tonosama no YabouCave StoryFreedom PlanetHigh Seas HavocMega Man SeriesMichael Jackson's MoonwalkerRistarSangokushi Retsuden: Ransei no EiyuutachiShinobi IIISonic SeriesTouhou Project Series

Sonic the Hedgehog Revelation (or Sonic Revelation) is a hack of Sonic 1 by Animemaster. This hack has many features and will continue to increase them, while the product is under way. It also plans a new zone, made of instruments known as music land. Although the creator hasn't decided on whether the art would be good enough yet. The hack contains the three hedgehogs Sonic, Shadow, Silver as they join to face Eggman once again.