Robert F. "Toby" Fox (born October 11, 1991) is an American indie game developer and composer. He is best known for creating and scoring the 2015 role-playing video game (RPG) Undertale, as well as Deltarune, a parallel story to Undertale released in chapters since 2018, with five of its planned seven chapters released as of October 2026. Fox developed Undertale almost entirely by himself, and it has been ranked in numerous publications as one of the greatest video games.
Born in Manchester, New Hampshire, Fox was significantly influenced by the RPG EarthBound during his childhood, and used RPG Maker to create games with his brothers. Inspired by Starmen.net, an EarthBound fan site, Fox began creating ROM hacks of EarthBound under the username Radiation, releasing the EarthBound Halloween Hack in 2008. Largely a self-taught musician, Fox relearned the piano during middle school to play video game music, and joined the music team for Homestuck, a webcomic by Andrew Hussie, in 2010.
During his time at Northeastern University in Boston, Fox conceived Undertale and Deltarune, and successfully raised funds for the former's development through Kickstarter in 2013. Fox continued to develop Undertale until its release two years later, while simultaneously planning Deltarune. He has composed music for various indie games and musicians, as well as the Pokémon franchise, and became involved with the Japanese game industry through connections with developers. Fox has also supported various charities and launched charity fundraisers related to his games.
Early life Robert F. Fox was born on October 11, 1991, in Manchester, New Hampshire, the third of four brothers. Fox discovered the RPG EarthBound at four years old, when he stated it was gifted to one of his older brothers for "Christmas or his birthday", and credited the game with helping him learn how to read. Around age five, he often drew fictional stage layouts based on the Mega Man X series during church services. While Fox attended elementary school, his brothers told him about RPG Maker 2000—a program used to develop RPGs—and they began creating games together using it, including Toby's Adventure, Fox's first game. Fox learned about the Touhou Project franchise through a free games website at age 10, and played the demo versions of Embodiment of Scarlet Devil and Perfect Cherry Blossom following a friend's recommendation.
Fox's interest in EarthBound was furthered at age 11 after discovering a fan site for the game, Starmen.net, which motivated him to create games to impress the site's members. Using the ROM hack editor PK Hack, which he considered his "entrance into [the] community", Fox created his first hack in middle school. Under the username Radiation, he released EarthBound Halloween Hack in 2008 as part of a ROM hacking competition on Starmen.net, and composed the song "Megalovania" for the hack's soundtrack. When Fox was disallowed by his parents from attending a yearly Starmen.net forum meetup due to his age, its founder Reid Young advised Fox to threaten to "smoke a cigarette" if he was not allowed to attend, which worked. Fox discovered the English fan translation of the RPG OFF through the site.
Primarily a self-taught musician, Fox began relearning the piano during middle school to play video game music he knew by ear, having previously taken lessons in second grade; he also played the trumpet through high school. Fox told Touhou Project creator ZUN in an interview that he had received a standing ovation following a piano rendition of "Necrofantasia" from Perfect Cherry Blossom during a high school summer camp gathering. As a high school senior, he began creating piano covers of music from the webcomic Homestuck, gaining recognition from its creator Andrew Hussie, joining the music team in 2010 and later becoming its production coordinator. Fox is a graduate of Northeastern University, where he studied environmental science.
Career Undertale (2015)
During his third year of university, Fox was inspired to create Undertale in December 2012 after reading a Wikipedia article about the array data structure, later using it to program text and battle systems for an RPG. Development on Undertale started during a break from his classes in 2013, and Fox prioritized creating the game's battle system first. Undertale initial development began out of Hussie's basement while Fox simultaneously worked on the Homestuck soundtrack. Fox discovered Temmie Chang's blog while looking for an artist, and despite having never talked to her before, Fox asked Chang if she wanted to create a game together, to which she agreed. Fox also began writing down design notes and sketching character designs in his school notebook.
Undertale demo was released in May 2013. Fox created a Kickstarter campaign for Undertale that June with a goal of $5,000, slating the game for a summer 2014 release; the funding goal was met the day of the Kickstarter's launch. The campaign ultimately raised over ten times that amount by its conclusion on July 24, totaling $51,124 from 2,398 people. Though Fox was initially "unsure if it was humanly possible to create [Undertale] before making the demo," he considerably expanded the game's scope following the demo's release. During Undertale development in 2014, Fox received his university degree. Fox used the Kickstarter's proceeds to continue working on the game until its release in September 2015. Undertale was Fox's "first full game", and he developed it almost entirely by himself, with Chang serving as the game's lead artist.
Undertale was released on September 15, 2015, to widespread critical acclaim, and has been ranked by numerous publications as one of the best video games of all time. Additionally, the Undertale soundtrack has been named one of the best video game soundtracks. Upon its release on Steam, Undertale rapidly gained popularity, selling over 500,000 copies within three months and doubling to one million copies two months later. In GameFAQs's December 2015 "Best. Game. Ever." poll, Undertale won against The Legend of Zelda: Ocarina of Time, the incumbent game from a similar 2009 poll, in a final vote of 156,000 participants. The game was nominated for various other accolades at game award ceremonies following its release, including at the D.I.C.E. Awards, The Game Awards, and the Game Developers Choice Awards.
The rapid rise of the Undertale fandom and its behavior towards those who disliked the game led Fox to comment about the matter on Twitter in January 2016, writing, "It's OK if people don't like the game. I don't care," and expressing hope the game would have an "overall good effect on the world". The next month, Fox gave his approval for Undertale Yellow, an Undertale fan game which would release over seven years later due to a period of development hell. That May, internet personality MatPat, the then-host of YouTube series Game Theorists, gifted Pope Francis a Steam key of Undertale during a meeting between the Pope and numerous other YouTubers.
Before Undertale first anniversary, Fox made a retrospective post on Tumblr describing his feelings about the game's success and the stress the attention brought him, further referring to Undertale as "about an 8/10, niche RPG game." The Undertale Art Book, which contained concept art and development commentary from Fox, was released through Fangamer in November 2016. Fox was included on Forbes 2018 list of 30 Under 30 in Games in November 2017 for his work on Undertale. During a making-of interview about Undertale with Edge in January 2018, Fox expressed happiness that many people were able to enjoy Undertale, including children excited about the game, though he remarked "my life has changed permanently and will never change back."
Deltarune (2018–present)
While sick at home from university in 2011, Fox had a fever dream about an ending for a video game, after which he became obsessed with making that game and created the concept for Deltarune in 2012, though he abandoned development before creating a single room. Some of the music from the concept became part of Undertale soundtrack, and as the game's Kickstarter campaign was underway, Fox decided his next game would be "a mix of Undertale and that dream concept." Fox began working on Deltarune demo, which became the game's first chapter, in 2014. Over the next year, prior to Undertale release, Fox began creating concept art and sketches for Deltarune main characters. Fox planned content for later parts of the game up to a decade in advance.
On October 30, 2018, Fox asked "those who completed Undertale" to view the official Undertale Twitter account. The next day, Fox unveiled a "survey program" available for free through the deltarune.com website, which was revealed to be Deltarune first chapter. Fox subsequently explained on Twitter that Deltarune was separate from Undertale world, and that no work beyond the first chapter had been done; he further sought to assemble a development team to assist him with creating the game. Although Fox continued writing dialogue and composing music, he disclosed in a February 2019 Indie World interview that Chapter 2's progress was "effectively 0%", and its development team had not yet been formed. For Undertale fourth anniversary, Fox shared new songs from Deltarune, further announcing progression in the game's design.
Fox had long suffered from chronic hand and wrist pain, though his symptoms became severe during Deltarune Chapter 2's development in early 2020, which made it difficult for him to write and compose. Fox stated Deltarune overall outline had been completed in a September 2020 development update. While Chapter 1 was programmed solely by Fox, with Chang returning for art, the development team was expanded for Chapter 2 onwards, in order to speed up production and due to Fox's wrist issues. Chapter 2 was announced on a livestream hosted by Fangamer for Undertale sixth anniversary on September 15, 2021, and released two days later. Fox opted to release the chapter for free, stating "the world has been really tough for everybody recently," though added the game's full release would be paid and was "definitely going to cost more than Undertale." Fox stated that Chapters 3–5 would be made available simultaneously after the game's paid release, and Deltarune would span seven chapters.
In November 2022, Fox started an email mailing list that allowed others to sign up for a seasonal Undertale / Deltarune newsletter featuring new information about Deltarune, with its first issue being released the following month. Further development updates were provided between newsletters, with Fox stating in the Halloween 2023 issue that work on Chapter 3 was "nearing completion", also revealing that Deltarune paid version would be available for purchase after Chapter 4 was finished, rescheduling Chapter 5 for a later release.
Following more updates via the newsletter throughout 2023 and 2024, Fox confirmed in late 2024 that Chapters 3 and 4 would "100% come out in 2025". Their release date was announced in the April 2025 Nintendo Direct for the Nintendo Switch 2, releasing them bundled in with the first two as a paid game on June 4, 2025, serving as a Nintendo Switch 2 launch title. Fox confirmed that future chapters would be free updates to the paid game, and revealed that Chapter 5 was planned to release in 2026. On June 9, 2026, Chapter 5 appeared in a Nintendo Direct, where its release date of June 24 was announced. The same month, Fox also stated that Chapter 6 was planned to release in 2027, and projected Chapter 7's development to begin before the end of 2026.