Extra stages, also referred to as EX Stages or Advanced Stages, are seven optional stages in Sonic Forces. These stages can be unlocked by collecting Red Star Rings. Finishing an extra stage will reward the player with extra Avatar items and offer bonus experience for the Avatar.
Extra stages have the same gameplay mechanics as regular stages in Sonic Forces and the same objectives (reaching the goal within a time limit). However, each extra stage is much shorter than regular stages regarding size and duration, being similar to the Challenge Acts from Sonic Generations and the smaller Acts in Sonic Colors. Like secret stages, they are also always played from a 2.5D perspective, and each puts special emphasis on a particular gimmick or obstacle, such as Sprinklers or dangerous cannons. However, extra stages are much tougher to complete than secret stages. The majority of the routes the player travels along in an extra stage are likewise different from those in regular stages, having been constructed from the ground up with additional plaforms and basic building blocks, such as Unbreakable Containers.
Extra stages are unlocked after the player collects a certain amount of Red Star Rings that coincide with the amount in the Challenge Missions. The area on the World Map (the stage select screen) where the respective extra stage is located determines its landscape. Completing all the extra stages pushes Team Sonic's occupied territory on the World Map past 99.9 percent and all the way up to 119.9 percent, though this does not erase Team Eggman's remaining 0.1 percent. It is also worth noting that only Sonic the Hedgehog and the Avatar are playable in the extra stages. Shadow the Hedgehog also becomes playable in the extra stages if the player has downloaded Episode Shadow.
On the World Map, the Stage Targets for extra stages are marked with a five-pointed star.