Undertale is a 2015 2D role-playing video game created by American indie developer Toby Fox. Undertale is notable for its use of multiple endings that change depending on the player’s actions. The goal of this TAS is to achieve each of the major variations in the endings, 10 of them in total. This allows for a diverse mix in the gameplay, as a lot of aspects that are normally skipped become required. For example, one of the main branching qualifications in the Neutral endings is which of the main bosses are left alive (besides Asgore who dies in all Neutral endings). Normally in Neutral speedruns, all four main bosses are left alive, but in All Major Endings, boss kills are part of the route.

The multiple branching endings also create opportunities for clever routing to save time. For example, one could save before Mettaton, kill Mettaton, and get an ending, then reload, skip Mettaton, and get a different ending. The unique route resulting from optimizing these routing decisions is what makes this an attractive and interesting way to speedrun the game.