This is our own personal chronological timeline for Sonic the Hedgehog and his universe, created and researched by the Sonic Metropolis Team. We spent many hours, days, and even months to figure out which timeline could be the most canon and logical one we can make. Keep in mind though that it is not perfect, because we also came to the conclusion that creating a 100% true Sonic timeline is impossible, because there will be always little details or facts which will speak against this timeline. However, this does not stop us from making the most logical timeline we can offer.
You also need to keep in mind that not all games or cartoons can be always canon of course, so we also sorted games out which are canon, and which are not. Furthermore we will not include Mini-, Party- or mobile games just as all other different sonic game versions ported from the one console to the other, and same for national changed versions [We always pick the original JAP variant]. If you however disagree with something, or you think you might found some issues with our timeline, you can always contact us about that, or create a forum post where we could discuss about your theory.
Team Sonic Metropolis
The Main Chronological Timeline
Notes About the Main Timeline
● Neither Classic Sonic nor Robotnik knew about the 7th Chaos Emerald in Sonic the Hedgehog 1. The 7th Chaos Emerald was later discovered in Sonic the Hedgehog 2.
● Some People consider Sonic the Hedgehog 2 being the second game in the Main Timeline, but that is incorrect. In Fact Sonic CD’s concepts and its project already started directly after Sonic the Hedgehog 1, and was planned to be released before Sonic the Hedgehog 2, but it was delayed. More evidence is manifested when you take note that the idle and some running sprites are the same as Sonic 1; in addition, the spin dash took a different form. In the original version you see also at the end of the game an image that shows up with Tails on it saying “See You Next Game” as reference to Sonic the Hedgehog 2.
● Sonic the Hedgehog 3 and Knuckles is a game which contains Sonic the Hedgehog 3 and Sonic & Knuckles. It has some differences though compared to the versions before, like you can play Sonic the Hedgehog 3 levels with Knuckles, or use Tails in the Levels of Sonic & Knuckles.
● To the Point of Sonic Adventure, all the characters aged a bit. Keep in Mind though that Sonic and his Friends are non-human, they have a complete different age system and play by other rules than humans do. Its unknown at what age the character are considered to be mature enough to be viewed as adult. What we know though is that all non-human characters become much faster mature than humans.
● The Shadow who appeared for the first time in Sonic Adventure 2 is the same Shadow who also did show up in all other Sonic Games. He did not die in Sonic Adventure 2; he was saved by Eggman and recovered.
● Even though Sonic the Hedgehog 2006 isnt canon when it does come to its plot or Silver’s and Blaze’s origin, it has some elements which do lead into some character development, for example that Shadow the Hedgehog and Omega did start now to work for GUN.
● Silver the Hedgehog is a character who came from the “Future” and even though its confirmed by SEGA that he indeed is from the future, it is very unlikely that this could work. (Warning, the following words are now only the opinion of the Administrator). Time Travel does not work at all in any points of being logical, especially in the Universe of Sonic the Hedgehog. Since Time Travel means automatically that a character can exists a billion times and even more just by going one millisecond back in time and taking the past version with you. Beside that even if you could go back in time to “fix things”, it will not change anything anyway from the current future you are from because each life form is or was an unique existence with its very own history and cannot be simply replaced, removed, or moved from one moment to another. That is why we Team Sonic Metropolis believe that Silver does not came from the future but from another Dimension instead, even though he believes he is, but he is likely wrong.
● Eggman Nega from Rush and Rivals are most probably two different personalities with different backstory and characteristics. Its basically impossible to have another logical explanation rather than Eggman Nega from Rush and from Rivals to be different characters, since there is no other way to explain their completely different backstory. We cannot name Rush or Rivals uncanon because of how both game do heavily affect the further Sonic game universe.
● Since the Events of 06 were deleted, Silver was introduced once again to Sonic and his friends in Rivals, in a more proper canon way.
● When it comes to the Storybook games “Sonic and the Secret Rings” and “Sonic and the Black Knight”, they are canon because of some little references to them in future Sonic games like Generations. However the only logical way of Sonic ending up in those 2 Worlds / Dimension, is that everything was only a Dream of his. We can exactly see how Sonic did fall asleep at the beginning of “Sonic and the Secret Rings” while he was reading just before that the Book of “Arabian Nights”. Also people do tend to dream about other people in different forms, that would also explain why many of his “new” companions or friends in those 2 games were his classic real friends. Furthermore, only Sonic knows about these happenings which further confirms that it was only a dream. So it might make sense that “Sonic and the Black Knight” was also just some imagination of Sonic while sleeping.
● Instead of the Wii Version, the DS one of Sonic Colors is probably the real canon one. Both games have the same plot, but however the handheld version does show you much more story elements and does also include more character interactions just as some other details like the appearance of the Mother Wisp. And on top of that, here is a little fun fact; Sonic Colors on the DS was originally meant to be called “Sonic Rush 3”. The Gameplay style does make it also quite obvious.
● In Sonic Generations we meet Classic Sonic once again, but most people mistake him with the Classic Sonic from “Sonic the Hedgehog 1” – “Sonic & Knuckles”. They are not the same individual, the Classic Sonic from Generations does come from another Dimension instead of the past, it was also later on confirmed in “Sonic Forces”.
● The Classic Sonic from the another Dimension is the playable in “Sonic Mania” and in “Sonic Forces”. He is not from the past, and has no connection to classic or modern Sonic at all.
Events Which Might Maybe Happened
These listed Events / Games count as being maybe part of the main timeline. However there are still either not enough or no proofs at all to confirm it.
Events Which Might Maybe Not Happened
These listed events and games are very unlikely to be canon in the same Universe as the main timeline, either because of crossovers or big plot holes.
Sonic Boom Universe
The Sonic Boom Universe is not connected with the main timeline in any way.
[Story Version 1]
[Story Version 2]
Definitely Not Connected To Main Timeline
These listed events and games are not in relationship with the main timeline for sure
TV Shows And Movies
● Adventures of Sonic the Hedgehog (1993-1995)
● Sonic the Hedgehog [SatAM] (1993–1994)
● Sonic the Movie [Sonic OVA] (1996, 1999)
● Sonic Underground (1999)
● Sonic X (2003–2006) [Plot and Human Characters are not Canon, however this show does represent many characters excellent in their, behavior, life style, hobbies and relationships to each other, when it does come to canon terms]
● Sonic: Night of the Werehog (2008)
● Sonic Boom (2014–2017)
● Sonic the Hedgehog 
Notes About TV Shows And Movies
● Adventures of Sonic the Hedgehog, Sonic the Hedgehog [SatAM] and Sonic Underground are cartoon shows which do show the biggest differences compared to the games, because they go into a completely other Universe direction than the games do.
● Sonic Underground is the only cartoon which is based to be a musical-styled show with Sonic and company.
● Sonic Night of the Werehog is the only short listed here.
● Sonic X is not fully canon, however its confirmed that Sonic Team wanted to show us more of the private life of each character, how their daily life in free time is like, and generally get more deep characteristics out of Sonic and his Friends. Its plot and the human characters are NOT canon, however most of the characteristics, the relationships between Sonic and his Friends, the abilities or skills, the way they spend their free time, and the way they behave is canon.
Furthermore Its important to mention that the Japanese version is the original one. The EU and US version are heavily edited, where much is cut and changed in terms of conversations, fights, environment details, music and emotions.
● Sonic Boom does play in the Boom Universe obviously. Its not connected to any other Universe at all.
● Sonic the Hedgehog 2020 does give us once again another spin off as far as canon ideas. Its just as the most other cartoons or movies not canon. It is Sonic’s debut on the big screen and boasts the highest opening for a video game movie ever along with several other feats.
Comics and Mangas
To get on point, there are no canon Comics or Mangas out there for Sonic the Hedgehog. All Comics and Mangas do play in a completely different Universe and are not even in the slightest connected to the Main Timeline.[Included : all Archie Comics, all Fleetway Comics, all IDW Comics, and different Mangas from Japan]
However, there may be some exceptions for some mini comics from SEGA, but these are only exceptions. In general there are no canon Comics or Mangas no matter its publisher.