Anyone backing at $10 or more would receive a digital download of the game. Those backing at $30 would receive the digital download of the game, have their name included in the True Pacifist Ending Credits, plus the game's soundtrack with a vocal bonus track by Papyrus called "Papyrus's Cool Song." Two joke tiers were included at $31 where a backer could receive all $30-tier prizes without the vocal track and $32 where a backer could receive all $30-tier prizes except with a version of the soundtrack that only has the vocal track. Backing at $50 or more earns all of the $30-tier prizes plus a sticker sheet, and backing at $75 would earn all of the $50-tier rewards plus physical CD of the game and its soundtrack.
Backing the Kickstarter at $100 or more would reward the backer with all of the $75-tier rewards and a special prize:
- At $100 or more, Tuyoki will make an overworld sprite of the backer's choice. (10 only)
- At $250 or more, a custom non-playable character would be included in the game. (6 only)
- At $500 or more, a custom character that is fightable can be included in the game. (2 only)
- At $1,000 or more, the backer's fantroll will become canon in Undertale. (1 only)
The Undertale Kickstarter campaign included a couple of stretch goals if the campaign was funded above its initial goal of $5,000. All of the stretch goals listed below were reached with the campaign being funded at $51,125.
- $7,500 - Expanded instruction manual
- $10,000- Macintosh Port by Leon Arnott
- $12,500 - SECRET BOSS (!?!)
- $17,500 - Monster designs by Magnolia Porter
- $20,000 - Patches and Wallpapers!
- $25,000 - Kickstarter-exclusive Undertale Remixes!!!
- $32,500 - Undertale Alarm Clock App
- $37,500 - Undertale Concept Art
- $45,000 - Undertale Extra Comics and/or Another Game
- The fightable monsters were later revealed to be Glyde and Muffet.
- The fantroll was later revealed to be So Sorry.
- The $1000 tier was a reference to the Homestuck Kickstarter.
- In this video, at one point, Sans talks with proper capitalization.