# Undertale

Undertale is a 2015 role-playing video game created by American indie developer Toby Fox. The player controls a child who has fallen into the Underground: a large, secluded region under the surface of the Earth, separated by a magical barrier. The player meets various monsters during the journey back to the surface, some of which may engage in combat. The combat system involves the player navigating through mini-bullet hell attacks by the opponent. They can opt to pacify or subdue monsters in order to spare them instead of killing them. These choices affect the game, with the dialogue, characters, and story changing based on outcomes.
Outside of artwork and character designs by Temmie Chang and other guest designers, Fox developed the entirety of the game by himself, including the script and music. The game took inspiration from several sources, including the Brandish, Mario & Luigi, and Mother role-playing game series, bullet hell shooter series Touhou Project, role-playing game Moon: Remix RPG Adventure, and British comedy show Mr. Bean. Undertale was originally meant to be two hours in length and was set to be released in mid-2014, but experienced delays.
The game was released for OS X and Windows in September 2015. It was also ported to Linux in July 2016, PlayStation 4 and PlayStation Vita in August 2017, the Nintendo Switch in September 2018, and Xbox One in March 2021. The game was acclaimed for its thematic material, intuitive combat system, musical score, originality, story, dialogue, and characters; however, the reaction to its art style was mixed. The game has sold at least five million copies and was nominated for multiple accolades and awards. Several gaming publications and conventions listed Undertale as game of the year, and others have since listed it as one of the greatest video games ever made. Two chapters of a related game, Deltarune, were released in 2018 and 2021.

## Gameplay

Undertale is a role-playing video game that uses a top-down perspective. In the game, the player controls a child and completes objectives in order to progress through the story. Players explore an underground world filled with towns and caves, and are required to solve numerous puzzles on their journey. The underground world is the home of monsters, many of whom challenge the player in combat; players decide whether to kill, flee from, or befriend them. Choices made by the player radically affect the plot and general progression of the game, with the player's morality acting as the cornerstone for the game's development.
When players encounter enemies in either scripted events or random encounters, they enter a battle mode. During battles, players control a small heart which represents their soul, and must avoid attacks unleashed by the opposing monster similar to a bullet hell shooter. As the game progresses, new elements are introduced, such as colored obstacles, and boss battles which change the way players control the heart. Players may choose to attack the enemy, which involves timed button presses. Killing enemies will cause the player to earn EXP (in turn increasing their LOVE) and gold. They can use the ACT option to check an enemy's attacking and defending attributes as well as perform various other actions, which vary depending on the enemy. If the player uses the right actions to respond to the enemy, or attacks them until they have low HP (but are still alive), they can then choose to spare them and end the fight without killing them. For some boss encounters to be completed peacefully, the player is required to survive until the character they are facing has finished their dialogue. The game features multiple story branches and endings depending on whether players choose to kill or spare their enemies; and as such, it is possible to clear the game without killing a single enemy.
Monsters will talk to the player during the battle, and the game will tell the players what the monster's feelings and actions are. Enemy attacks change based on how players interact with them: should players choose non-violent options, enemy attacks are comparatively easy, whereas they become less easy if players choose violent options. The game relies on a number of metafictional elements in both its gameplay and story. When players participate in a boss battle on a second playthrough, the dialogue will be altered depending on actions in previous playthroughs.

## Plot

Undertale is set in the Underground, a realm where monsters were banished after war broke out with humans. The Underground is sealed from the surface by a magic barrier with a singular gap at Mount Ebott. A human child falls into the Underground from Mount Ebott and encounters Flowey, a sentient flower who teaches the player the game's mechanics and lies about "LV", or "LOVE", in an attempt to kill them. The human is rescued by Toriel, a motherly goat-like monster, who teaches them how to survive conflict in the Underground without killing. She intends to adopt the human, wanting to protect them from Asgore, the king of the Underground.
The human eventually leaves Toriel to search for Asgore's castle, which contains the barrier to the surface world. They encounter several monsters, such as the skeletons Sans and Papyrus, two brothers who act as sentries for the Snowdin forest; Undyne, the head of the royal guard; Alphys, the kingdom's royal scientist; and Mettaton, a robotic television host Alphys created. Most of the monsters are fought, with the human choosing whether to kill them or to spare and possibly befriend the monster. During their travels, the human learns that many years ago, Asriel, the son of Asgore and Toriel, befriended the first human who fell into the Underground. When the child abruptly died, Asriel used the child's soul to pass through the barrier, intending to return the body to the surface. The humans living there attacked and killed Asriel, causing Asgore to declare war. In the present day, Asgore has collected six souls from fallen humans, of which he needs one more to destroy the barrier.
The game's ending depends on how the player handles encounters with monsters. If the player completes a playthrough without killing any monsters (or killed some but not all of the monsters) they experience the "Neutral" ending. The human arrives at Asgore's castle and is forced to fight him. Sans stops the human before their confrontation, revealing that the human's "LOVE" and "EXP" are acronyms for "level of violence" and "execution points", respectively. Sans judges the human based on their accumulated "LOVE" and "EXP". The human then fights Asgore, but Flowey interrupts, killing Asgore, stealing the human souls and transforming into a more powerful form with their power. During this battle, the human calls the souls for help in weakening Flowey. After the battle, the human leaves the Underground. They then receive a phone call from Sans, detailing the state of the Underground after the human's departure, with the specifics depending on who was killed or spared.

### Pacifist

If the player kills no monsters before completing a "Neutral" ending, they can reload their saved game to complete the "Pacifist" ending. Flowey is revealed to be a reincarnation of Asriel accidentally created by Alphys's experiments. During the fight with Asgore, Toriel stops the battle and is joined by the other monsters the human befriended. Flowey ambushes the group, absorbing the souls of all the humans and monsters in order to take an older Asriel's form. During the ensuing fight, the human manages to connect with the souls of their friends, and eventually defeats Asriel: He reverts to his child form, destroys the barrier, and expresses remorse for his actions before leaving, revealing the human's true name as Frisk. The human falls unconscious and is awoken to see their friends surrounding them. The monsters peacefully reintegrate with the humans, while the human has the option of accepting Toriel as their adoptive mother.

### Genocide/No Mercy

A third ending, known by fans as the "No Mercy" or "Genocide" ending, ensues if the player kills every single monster in the game that can be fought. This involves continuously triggering random encounters in each area until no more monsters remain. Going down this route changes many aspects of the game: the game's soundtrack becomes more ominous, and most other characters are absent from the Overworld, having evacuated to escape the player's rampage. The few remaining characters that can be interacted with have changed dialogue, reflecting the impact the player's actions are having on the game's world. When the human reaches Asgore's castle, Sans attempts to stop them, but fails and is slain. Flowey kills Asgore in an attempt to obtain mercy, but is killed by the human. Chara, the first fallen child who befriended Asriel, then appears and erases the world. To enable further replays of the game, the player must give their soul to Chara, restoring the world and causing a permanent alteration to the Pacifist ending.

## Development

Undertale was developed by Toby Fox across 32 months. Development was financed through a crowdfunding campaign on the website Kickstarter. The campaign was launched on June 25, 2013, with a goal of US$5,000; it ended on July 25, 2013, with US$51,124 raised by 2,398 people. Fox had little experience with game development; he and his three brothers often used RPG Maker 2000 to make role-playing games, though few were ever completed. Fox also worked on several EarthBound ROM hacks while in high school. Before the release of Undertale, he was best known for composing music for the webcomic Homestuck, starting in 2010. Undertale was the first full game that he wrote.
According to Fox, he was casually reading Wikipedia in December 2012 when he found its article for array data structures, something Fox did not have knowledge of. After reading the page, he thought about how he could use it to create a text system for an RPG. After completing it, he came up with the idea of creating a battle system. This system, which was created using the game creation system GameMaker: Studio, informed how Fox wrote the story, as both are intertwined. He wanted to develop a role-playing game that was different from the traditional design, which he often found "boring to play". He set out to develop a game with "interesting characters", and that "utilizes the medium as a storytelling device ... instead of having the story and gameplay abstractions be completely separate".
Fox worked on the entire game independently, besides some of the art; he decided to do so to avoid relying on others. Temmie Chang worked as the main artist for the game, providing most of the sprites and concept art. Fox has said that the game's art style would likely remain the same if he had access to a larger team of artists. He found that "there's a psychological thread that says audiences become more attached to characters drawn simply rather than in detail", particularly benefiting from the use of visual gags within the art. Retrospectively, Fox described Undertale as "a huge katamari of things that [he likes] that [he] combined arbitrarily", adding that part of the story "was almost written improvisationally at the last minute".

### Game design

The defensive segment within the battle system was inspired by the Mario & Luigi series, as well as bullet hell shooters such as the Touhou Project series. When working on the battle system, Fox set out to create a mechanic that he would personally enjoy. He wanted Undertale to have a battle system equally engaging as Super Mario RPG (1996) and Mario & Luigi: Superstar Saga (2003). Fox did not want grinding to be necessary at any point in the game, instead leaving it optional to players. He also did not wish to introduce fetch quests, as they involve backtracking, which he dislikes. In terms of the game's difficulty, Fox ensured that it was easy and enjoyable. He asked some friends who are inexperienced with bullet hell shooters to test the game, and found that they were able to complete it. He felt that the game's difficulty was optimal, particularly considering the complications involved in adding another difficulty setting.
The game's dialogue system was inspired by Shin Megami Tensei (1992), particularly the gameplay mechanic whereby players can talk to monsters to avoid conflict. Fox intended to expand upon this mechanic, as failing to negotiate resulted in a requirement to fight. "I want to create a system that satisfied my urge for talking to monsters", he said. When he began developing this mechanic, the concept of completing the game without killing any enemies "just evolved naturally". However, he never considered removing the option to fight throughout development. When questioned on the difficulty of playing the game without killing, Fox responded that it is "the crux of one of the major themes of this game", asking players to think about it themselves. Despite not having played it, Fox was inspired by the concepts of Moon: Remix RPG Adventure (1997), which involved the player repairing the damage of the "Hero" and increasing their "Love Level" by helping people instead of hurting them. Fox also cited Cave Story (2004) as a general inspiration for the game.

### Writing

According to Fox, the "idea of being trapped in an underground world" was inspired by the video game Brandish. Fox was partly influenced by the silliness of internet culture, as well as comedy shows like Mr. Bean.$^{:1:27:30}$ He was also inspired by the unsettling atmosphere of EarthBound. Fox's desire to "subvert concepts that go unquestioned in many games" further influenced Undertale's development. Fox found that the writing became easier after establishing a character's voice and mood. He also felt that creating the world was a natural process, as it expressed the stories of those within it. Fox felt the importance to make the game's monsters "feel like an individual". He cited the Final Fantasy series as the opposite; "all monsters in RPGs like Final Fantasy are the same ... there's no meaning to that".
The character of Toriel, who is one of the first to appear in the game, was created as a parody of tutorial characters. Fox strongly disliked the use of the companion character Fi in The Legend of Zelda: Skyward Sword, in which the answers to puzzles were often revealed early. Fox also felt that role-playing video games generally lack strong mother characters; in the Pokémon series, as well as Mother and EarthBound, Fox felt that the mothers are used as "symbols rather than characters". In response, Fox intended for Toriel's character to be "a mom that hopefully acts like a mom", and "genuinely cares" about players' actions. Initially, Toriel had to be killed in order to progress the game, but Fox changed it before the release of Undertale's demo.
Papyrus and Sans are named after the typefaces Papyrus and Comic Sans, and their in-game dialogue is displayed accordingly in their respective eponymous fonts. Both characters are listed in the game's credits as being inspired by J. N. Wiedle, author of Helvetica, a webcomic series about a skeleton named after the font of the same name. Papyrus in particular was conceived as a sketch in Fox's notebook; he was originally a mean spirited character named "Times New Roman" who wears a fedora.

### Music

The game's soundtrack was entirely composed by Fox with FL Studio. A self-taught musician, he composed most of the tracks with little iteration; the game's main theme, "Undertale", was the only song to undergo multiple iterations in development. The soundtrack was inspired by music from Super NES role-playing games, such as EarthBound, bullet hell series Touhou Project, and the webcomic Homestuck, for which Fox provided some of the music. Fox also stated that he tries to be inspired by all music he listens to, particularly those in video games. According to Fox, over 90% of the songs were composed specifically for the game. "Megalovania", the song used during the boss battle with Sans, had previously been used within Homestuck and in one of Fox's EarthBound ROM hacks. For each section of the game, Fox composed the music prior to programming, as it helped "decide how the scene should go". He initially tried using a music tracker to compose the soundtrack, but found it difficult to use. He ultimately decided to play segments of the music separately, and connect them on a track. To celebrate the first anniversary of the game, Fox released five unused musical works on his blog in 2016. Four of the game's songs were released as official downloadable content for the Steam version of Taito's Groove Coaster.
Undertale's soundtrack has been well received by critics as part of the success of the game, in particular for its use of various leitmotifs for the various characters used throughout various tracks. In particular, "Hopes and Dreams", the boss theme when fighting Asriel in the Pacifist run, brings back most of the main character themes, and is "a perfect way to cap off your journey", according to USgamer's Nadia Oxford. Oxford notes this track in particular demonstrates Fox's ability at "turning old songs into completely new experiences", used throughout the game's soundtrack. Tyler Hicks of GameSpot compared the music to "bit-based melodies".
The Undertale soundtrack has frequently been covered by various styles and groups. As part of the fifth anniversary of the game, Fox streamed footage with permission of a 2019 concert of the Undertale songs performed by Music Engine, an orchestra group in Japan, with support of Fangamer and 8-4.

## Release

Undertale's first demo was released on May 23, 2013, which at the time was said to account for about 25 percent of the full game. It had an initial release timeframe of Summer 2014. The game was released on September 15, 2015, for OS X and Windows, and on July 17, 2016, for Linux. Fox expressed interest in releasing Undertale on other platforms, but was initially unable to port it to Nintendo platforms without reprogramming the game due to the engine's lack of support for these platforms. A patch was released in January 2016, fixing bugs and altering the appearance of blue attacks to help colorblind players see them better. Sony Interactive Entertainment announced during E3 2017 that Undertale would get a release for the PlayStation 4 and PlayStation Vita, and a retail version published by Fangamer. These versions were released on August 15, 2017.
A Nintendo Switch version was revealed during a March 2018 Nintendo Direct, though no release date was given at the time; Undertale's release on Switch highlighted a deal made between Nintendo and YoYo Games to allow users of GameMaker Studio 2 to directly export their games to the Switch. The Switch version was released on September 15, 2018, in Japan, and on September 18, 2018, worldwide. The Xbox One version was released on March 16, 2021. As with the PlayStation 4 and Switch versions, the Xbox One version features unique content specific to that platform. All the console ports were developed and published by Japanese localizer 8-4 in all regions.

### Promotion

Other Undertale media and merchandise have been released, including toy figurines and plush toys based on characters from the game. The game's official soundtrack, Undertale Soundtrack, was released by video game music label Materia Collective in 2015, simultaneously with the game's release. Additionally, two official Undertale cover albums have been released: the 2015 metal/electronic album Determination by RichaadEB and Amie Waters, and the 2016 jazz album Live at Grillby's by Carlos Eiene, better known as insaneintherainmusic. Another album of jazz duets based on Undertale's songs, Prescription for Sleep, was performed and released in 2016 by saxophonist Norihiko Hibino and pianist Ayaki Sato.
A 2xLP vinyl edition of the Undertale soundtrack, produced by iam8bit, was also released in the same year. Two official UNDERTALE Piano Collections sheet music books and digital albums, arranged by David Peacock and performed by Augustine Mayuga Gonzales, were released in 2017 and 2018 by Materia Collective. A Mii Fighter costume based on Sans was made available for download in the crossover title Super Smash Bros. Ultimate in September 2019, marking the character's official debut as a 3D model. This costume also adds a new arrangement of "Megalovania" by Fox as a music track. Super Smash Bros. director Masahiro Sakurai noted that Sans was a popular request to appear in the game. Music from Undertale was also added to Taiko no Tatsujin: Drum 'n' Fun! as downloadable content.

### Japanese localization

After Undertale's release, a small Japanese fan community slowly emerged, leading to an unofficial fan localization patch being released in early 2016. Since Fox had envisioned a Japanese translation as an eventual goal while working on the game, he consulted a number of different companies, eventually choosing 8-4, which had previously translated Aquaria and Shovel Knight.
To ensure a consistent voice for the game, 8-4 chose to employ only one primary translator, Keiko Fuchicho, even though it would lead to the Japanese version taking longer to release. She was supported by a small team of editors and proofreaders, and a programmer which modified the game to work with Japanese writing systems. Before the translation began in early 2016, Fox provided development notes and annotated dialogue to the team, and he continued to support and advise them throughout its creation. As PC gaming is less prominent in Japan, they concurrently made the decision to release Undertale for consoles, with the porting also being handled by 8-4. After the localization's announcement, many fans were surprised by the decision to use the Japanese pronoun oira (おいら) for Sans due to its connotation with rural life, leading to the term oira shock. The localization was released for PS4 and Vita on August 16, 2017, and for PC on August 22.

## Reception

Aggregate score :
| Aggregator | Score |
| Metacritic | (PC) 92/100 (PS4) 92/100 (NS) 93/100 |
Review scores :
| Publication | Score |
| Destructoid | 10/10 |
| Game Informer | 9.5/10 |
| GameSpot | 9/10 |
| Giant Bomb | 5/5 |
| IGN | 10/10 |
| PC Gamer (US) | 91/100 |
| USgamer | 5/5 |
Undertale received "universal acclaim" from critics, according to review aggregator website Metacritic. There, it is the third-highest rated Windows game released in 2015, and among the top 50 of all time. It was temporarily the highest-rated PC game of all time on Metacritic after release. Praise was particularly directed at the game's writing, unique characters, and combat system. GameSpot's Tyler Hicks declared it "one of the most progressive and innovative RPGs to come in a long time", and IGN's Kallie Plagge called it "a masterfully crafted experience".
Daniel Tack of Game Informer called the game's combat system "incredibly nuanced", commenting on the uniqueness of each enemy encounter. Giant Bomb's Austin Walker praised the complexity of the combat, commenting that it is "unconventional, clever, and occasionally really difficult". Ben "Yahtzee" Croshaw of The Escapist commended the game's ability to blend turn-based and live combat elements. IGN's Plagge praised the ability to avoid combat, opting for friendly conversations instead. Jesse Singal of The Boston Globe found the game's ability to make the player empathize with the monsters during combat if they opted for non-violent actions was "indicative of the broader, fundamental sweetness at the core" of Undertale. Games and Culture's Gabriel Elvery believed the general appeal of Undertale's pacifist route was the facilitation of parasocial interactions with its monsters, which was attributed to their simplicity and representation of daily human life, constrasted to the genocide route, where such interactions cannot happen, as the monsters have either fled or were killed by the player.
Essayist Sean Travers in the Journal of Popular Culture described Undertale as a critique of the violent nature of mainstream role-playing video games, where players kill enemies in exchange for experience points. She noted the game's rather punitive nature towards those who choose to play through the Genocide route and ignore warnings, citing its progressive change in tone and disturbing imagery. Travers interprets this as the player becoming the antagonist or a "postmodern psychopath", which is described as a character who commits immoral actions for the sole reason being their consequences. She believed that Undertale is innovative in such games, due to the player's "degree of choice." Kevin Vale of Convergence compared Undertale's management of accountability to that of Night in the Woods, citing the central role the player has in them, while contrasting their use of gameplay elements.
Reviewers praised the game's writing and narrative, which IGN's Plagge labeled it as "strong" and "consistently funny" and noted how it "[built] on" Undertale's themes of humanity and morality. The Escapist's Croshaw considered Undertale the best-written game of 2015, writing that it "is on the one hand hilarious... and is also, by the end, rather heartfelt". Destructoid's Ben Davis praised the game's characters and use of comedy, and compared its tone, characters, and storytelling to Cave Story (2004). PC Gamer's Richard Cobbett provided similar comments, writing that "even its weaker moments... just about work". Undertale's absurd humor attracted praise; Kill Screen considered absurdity a signature quality of Fox's humor.
The game's visuals received mixed reactions. Giant Bomb's Walker called it "simple, but communicative". IGN's Plagge wrote that the game "isn't always pretty" and "often ugly", but felt that the music and animations compensate. The Escapist's Croshaw remarked that "it wobbles between basic and functional to just plain bad". Other reviewers liked the graphics: Daniel Tack of Game Informer felt that the visuals appropriately match the characters and settings, while Richard Cobbett of PC Gamer commended the ability of the visuals to convey emotion.

### Sales

By the end of 2015, according to a preliminary report by Steam Spy, Undertale was one of the best-selling games on Steam, with 530,343 copies sold. By early February 2016, the game surpassed one million sales, and by July 2018, the game had an estimated total of three and a half million players on Steam. Japanese digital PlayStation 4 and PlayStation Vita sales surpassed 100,000 copies sold by February 2018. By March 2019, Undertale was one of the ten best-selling indie games on the Switch. As of August 29, 2024, Steam Spy estimates that Undertale has sold between 5 and 10 million copies on Steam.

## Impact and legacy
### Fandom

Undertale quickly developed a cult following. About a year after release, Fox commented that he was surprised by how popular the game had become and though appreciative of the attention, he found it stressful. Fox said: "It wouldn't surprise me if I never made a game as successful again. That's fine with me though". Ana Diaz of NPR stated that Undertale "shaped the entertainment tastes of an entire generation", and that it "took on a new life through memes". Reid Young, CEO of Fangamer, said that the game became "an absolutely dominating force". The character Sans has been well received by players, being the subject of many fan works. Professional wrestler Kenny Omega has expressed his love of Undertale, dressing as Sans for the October 30, 2019, episode of All Elite Wrestling: Dynamite. Sans's addition as a Mii fighter costume in Super Smash Bros. Ultimate garnered positive feedback from fans, although The Commonwealth Times considered his addition to be a "potential problem" due to the decreasing nostalgia factor for each new character and ever-increasing size of the roster. The Undertale fandom has also been noted for the creations of various fan games that offer unique stories and gameplay mechanics based on the Undertale world. Among the most anticipated fangames was the spinoff Undertale Yellow, which after seven years of development was released in 2023 and met with immense popularity by fans on multiple social media networks.
Undertale's fanbase has also been subject to controversy, leading to it gaining a negative reputation. Part of it was due to the disagreement between fans over the correct way to play the game. After the game's release, some live streamers were harassed by fans of the game for killing in-game enemies and attempting the "genocide" route. YouTuber Markiplier refused to complete his initial play-through of the game, stating that he was "not having fun" due to fan demands.
In July 2016, during a summit about the Internet held at the Vatican, YouTube personality MatPat gifted a copy of Undertale to Pope Francis. MatPat explained his choice of gift by referencing the year 2016's status as the Extraordinary Jubilee of Mercy, and connecting this to Undertale's overarching theme of mercy. Later, in January 2022, a circus troupe performed in front of the Pope during his weekly audience at the Vatican to the tune of "Megalovania", drawing parallels with MatPat's symbolic gift of the game to Pope Francis. Christopher Cayari of the International Journal of Education & the Arts described Undertale's popularity as an example of video game music serving as a medium that could serve a great utility to music educators, citing the fandom's participatory culture.

#### Fan theories

Undertale's fandom has been among the most prone to fan theories due to the mysterious nature of many plot elements. A commonly proposed theory by the fandom is that Chara, the first human who fell into the underground and is credited to causing the destruction inflicted in the Genocide route, is the narrator of the game. Among all theories proposed by the fandom though, the story regarding the former royal scientist W. D. Gaster is often cited as the deepest rabbit hole in the story of the game. The Gaster story has very few pieces of evidence confirmed to have been known by the community outside of his association with the font Wingdings, his role as the royal scientist, and creating the CORE (a magical and technological power source for the Underground's monsters who live in the most populated areas) within Undertale only to "fall into his creation" and have his body shattered across time and space. Upon the release of Deltarune, players en masse speculated that Gaster played some role in the plot of the game and was an attempt to link both Undertale and Deltarune together aside from sharing the same characters.

### Accolades

The game appeared on several year-end lists of the best games of 2015, receiving Game of the Month and Funniest Game on PC from Rock Paper Shotgun, Best Game Ever from GameFAQs, and Game of the Year for PC from Zero Punctuation, and IGN. It also received Best PC Game from Destructoid.
Undertale garnered awards and nominations in a variety of categories with praise for its story, narrative and for its role-playing. At IGN's Best of 2015, the game received Best Story. The Academy of Interactive Arts & Sciences nominated Undertale for Role-Playing/Massive Multiplayer Game of the Year, Outstanding Achievement in Game Direction, and the D.I.C.E. Sprite Award. Undertale was nominated for the Innovation Award, Best Debut, and Best Narrative at the Game Developers Choice Awards. In 2016, at the Independent Games Festival the game won the Audience Award, and garnered three nominations for Excellence in Audio, Excellence in Narrative, and the Seumas McNally Grand Prize. The SXSW Gaming Awards named it the Most Fulfilling Crowdfunded Game, and awarded it the Matthew Crump Cultural Innovation Award. The same year at the Steam Awards the game received a nomination for the "I'm not crying, there's just something in my eye" award. In 2019, Polygon named the game among the decade's best. In 2021, IGN listed Undertale as the 20th greatest game of all time, while in Japan, a nationwide TV Asahi poll of over 50,000 players listed Undertale as the 13th greatest game of all time.
| Award | Date of ceremony | Category | Result |
| British Academy Games Awards | April 7, 2016 | Story | Nominated |
| D.I.C.E. Awards | February 18, 2016 | Role-Playing/Massively Multiplayer Game of the Year | Nominated |
| D.I.C.E. Awards | February 18, 2016 | D.I.C.E. Sprite Award | Nominated |
| D.I.C.E. Awards | February 18, 2016 | Outstanding Achievement in Game Direction | Nominated |
| Dragon Awards | August 11, 2016 | Best Science Fiction or Fantasy PC/Console Game | Nominated |
| Global Game Awards | November 27, 2015 | Best Indie | Runner-up |
| The Game Awards | December 3, 2015 | Best Independent Game | Nominated |
| The Game Awards | December 3, 2015 | Games for Change | Nominated |
| The Game Awards | December 3, 2015 | Best Role-Playing Game | Nominated |
| Game Developers Choice Awards | March 16, 2016 | Innovation Award | Nominated |
| Game Developers Choice Awards | March 16, 2016 | Best Debut | Nominated |
| Game Developers Choice Awards | March 16, 2016 | Best Narrative | Nominated |
| Independent Games Festival Awards | March 16, 2016 | Seumas McNally Grand Prize | Nominated |
| Independent Games Festival Awards | March 16, 2016 | Excellence in Audio | Nominated |
| Independent Games Festival Awards | March 16, 2016 | Excellence in Narrative | Nominated |
| Independent Games Festival Awards | March 16, 2016 | Audience Award | Won |
| Japan Game Awards | September 23, 2018 | Award for Excellence | Won |
| SXSW Gaming Awards | March 19, 2016 | Game of the Year | Nominated |
| SXSW Gaming Awards | March 19, 2016 | Excellence in Gameplay | Nominated |
| SXSW Gaming Awards | March 19, 2016 | Most Promising New Intellectual Property | Nominated |
| SXSW Gaming Awards | March 19, 2016 | Most Fulfilling Crowdfunded Game | Won |
| SXSW Gaming Awards | March 19, 2016 | Matthew Crump Cultural Innovation Award | Won |

### Deltarune

After previously teasing something Undertale-related a day earlier, Fox released the first chapter of Deltarune on October 31, 2018, for macOS and Windows for free. Deltarune is "not the world of Undertale", according to Fox, though characters and settings may bring some of Undertale's world to mind, and is "intended for people who have completed Undertale". The name Deltarune is an anagram of Undertale. Fox stated that this release is the first part of a new project, considering it a "survey program" to determine the project's future direction. Fox clarified that Deltarune will be a larger project than Undertale, stating it took him a few years to create the game's first chapter, much longer than it took him to complete the Undertale demo.
Chapter 2 of Deltarune was released on September 17, 2021, after Fox acquired a team to help him with further development. Once all chapters are complete, the game will be released as a complete whole; Fox stated that he does not have an anticipated timetable for completion. Deltarune is planned to have only one ending, regardless of what choices the player makes in the game. Although the first two chapters were released at no cost, Fox plans to charge players for the finished release.