Undertale is a role-playing video game released in 2015. It was created by Toby Fox, an independent game developer from the United States. In the game, players control a child who falls into the Underground, a large, hidden area beneath the Earth’s surface. This area is separated from the surface by a magical barrier. During the journey back to the surface, the player meets many monsters. Some of these monsters may fight the player. The combat system requires the player to avoid fast-moving attacks from opponents. Instead of fighting, players can choose to calm the monsters and spare their lives. These choices influence the game, changing the story, characters, and dialogue based on the outcomes.
Toby Fox designed most of the game himself, including the script and music. Temmie Chang and other guest artists created the artwork and character designs. The game was inspired by several sources, such as the Brandish, Mario & Luigi, and Mother role-playing game series, the Touhou Project bullet hell shooter series, the Moon: Remix RPG Adventure role-playing game, and the British comedy show Mr. Bean. Originally, Undertale was planned to be two hours long and released in mid-2014, but it faced delays.
Undertale was first released for OS X and Windows in September 2015. It later became available on Linux in 2016, PlayStation 4 and PlayStation Vita in 2017, Nintendo Switch in 2018, and Xbox One in 2021. The game received praise for its themes, combat system, music, originality, story, dialogue, and characters. However, opinions about the art style were divided. Undertale has sold at least five million copies. It was nominated for many awards, including "Game of the Year" from several gaming publications and conventions. It is considered one of the greatest video games ever made. A game with a similar story, Deltarune, began releasing episodes in 2018 and is set to be fully released in 2025. Additional chapters are currently being developed.
Gameplay
Undertale is a role-playing video game that uses a view from above. In the game, the player controls a child and completes tasks to move forward in the story. Players explore an underground world with towns and caves, and solve many puzzles along the way. This underground world is home to monsters, who challenge the player in battles. During these battles, players decide whether to fight, run away, or make friends with the monsters. The choices the player makes greatly change the story and how the game progresses, with the player's decisions about right and wrong shaping the game's development.
When players meet enemies in planned events or random battles, they enter a battle mode. During battles, players control a small heart that represents their soul and must avoid attacks from the monster, similar to a game where you dodge many bullets. As the game progresses, new features are added, such as colored obstacles and boss battles that change how players control the heart. Players may choose to attack the enemy by pressing buttons at the right time. Killing enemies gives the player EXP, which increases their LOVE, and gold. They can use the ACT option to see an enemy's attack and defense strengths and perform other actions that depend on the enemy. If the player uses the correct actions to respond to the enemy or attacks them until they have low HP but are still alive, they can choose to spare them and end the fight without killing them. To complete some boss battles peacefully, the player must survive until the enemy finishes speaking. The game has different story paths and endings based on whether players choose to kill or spare enemies; it is possible to finish the game without killing any enemies.
During battles, monsters speak to the player, and the game shows players the monster's feelings and actions. Enemy attacks change based on how players interact with them and the difficulty level. The game includes elements that reference the game itself in both its gameplay and story. When players fight a boss on a second playthrough, the dialogue changes based on actions taken in earlier playthroughs.
Plot
Undertale takes place in the Underground, a place where monsters were sent after a war with humans long ago. The Underground is protected by a magical barrier that only has one opening at Mount Ebott. At the beginning of the game, a human child falls into the Underground through Mount Ebott and meets Flowey, a flower that can think and speak. Flowey teaches the player how to play the game but lies about "LV," or "LOVE," to try to harm the player. The child is then rescued by Toriel, a kind monster who looks like a goat. Toriel helps the human learn how to survive in the Underground without fighting or killing. She wants to adopt the human to protect them from Asgore, the king of the Underground.
The human leaves Toriel to find Asgore’s castle, which holds the barrier to the surface world. Along the way, the human meets many monsters, including Sans and Papyrus, two skeleton brothers who guard Snowdin Forest; Undyne, the leader of the royal guard; Alphys, the kingdom’s scientist; and Mettaton, a robot created by Alphys. The human must decide whether to fight and kill these monsters or try to spare and befriend them. During their journey, the human learns about Asriel, the son of Asgore and Toriel, who once befriended the first human who fell into the Underground. When that human died, Asriel used their soul to try to return their body to the surface. This act led to a war between humans and monsters. Today, Asgore has collected six souls from humans who have died and needs one more to destroy the barrier.
The game’s ending depends on the player’s choices. If the player kills some monsters or none at all, they reach the "Neutral" ending. The human arrives at Asgore’s castle and must fight him. Sans, one of the monsters, stops the fight and explains that "LOVE" and "EXP" stand for "level of violence" and "execution points," which measure how many monsters the player has killed. Flowey, the flower, then attacks and kills Asgore, becoming more powerful by absorbing the souls of humans and monsters. With the help of monsters who were spared, the human defeats Flowey and can choose to kill or spare him. Afterward, the human leaves the Underground and later receives a phone call from Sans, who updates them about the Underground’s condition.
If the player kills no monsters during the Neutral ending, they can restart the game to achieve the "True Pacifist" ending. Flowey is revealed to be a reborn version of Asriel created by Alphys. Before fighting Asgore, Toriel stops the battle and is joined by monsters the human befriended. Flowey attacks, absorbing the souls of humans and monsters to take the form of an older Asriel. The human connects with their friends’ souls and defeats Asriel, who reverts to his child form, destroys the barrier, and leaves, revealing the human’s name as Frisk. The human wakes up to find their friends around them, and the monsters and humans live peacefully together. The human can choose to accept Toriel as their adoptive mother.
A third ending, called the "No Mercy" or "Genocide" ending, occurs if the player kills every monster. To reach this ending, the player must fight all monsters repeatedly until none remain. This changes the game: many characters leave, and those who stay have dialogue that shows the impact of the player’s actions. When the human reaches Asgore’s castle, Sans tries to stop them but is killed. Flowey kills Asgore to try to gain mercy but is killed by the human. Chara, the first human who befriended Asriel, appears and destroys the world. To replay the game, the player must give their soul to Chara, which permanently changes the True Pacifist ending.
Development
Undertale was created by Toby Fox over 32 months. The game was funded through a campaign on Kickstarter, a website where people donate money to support projects. The campaign started on June 25, 2013, with a goal of raising US$5,000. It ended on July 25, 2013, with US$51,124 collected from 2,398 people. Toby had little experience in game development before Undertale. He and his brothers often used RPG Maker 2000 to make role-playing games, but few were completed. Toby also worked on EarthBound ROM hacks during high school. Before Undertale, he was known for writing music for the webcomic Homestuck, starting in 2010. Undertale was his first full game. The name "Undertale" was inspired by the names of EarthBound and Homestuck, which are made up of two words combined. Toby wanted a name that was catchy. Another influence was the game Cave Story, where he changed "Cave" to "Under" and "Story" to "Tale" because they have similar meanings.
Toby was reading Wikipedia in December 2012 when he learned about array data structures, a way to organize information in computer science. He thought about how to use this idea to create a text system for an RPG. After completing it, he developed a battle system using GameMaker: Studio, a game creation tool. This system influenced how he wrote the story, as both were connected. Toby wanted to make a role-playing game that was different from traditional designs, which he found boring despite loving JRPGs. He aimed to create a game with interesting characters and use the game as a storytelling tool, not just separate from gameplay.
Toby worked on the game alone, except for some art. He chose to do this to avoid depending on others. Temmie Chang was the main artist, creating most of the sprites and concept art. Toby said the art style would likely stay the same even with a larger team. He believed simple characters make audiences more attached to them, especially with visual jokes in the art. Looking back, Toby described Undertale as a mix of things he liked, combining them in unexpected ways. He said part of the story was written last-minute.
The defensive part of the battle system was inspired by games like Mario & Luigi and bullet hell shooters such as Touhou Project. Toby wanted to create a mechanic he would enjoy. He aimed for a battle system as engaging as Super Mario RPG and Mario & Luigi: Superstar Saga. He did not want grinding, or repeating tasks for experience, to be necessary, making it optional. He also avoided fetch quests, which require backtracking, something he disliked. Toby ensured the game was easy and fun, testing it with friends who were new to bullet hell shooters. He felt the difficulty was just right, as adding another difficulty setting would have been complicated.
The dialogue system was inspired by Shin Megami Tensei, where players can talk to monsters to avoid fighting. Toby wanted to expand this idea, making negotiation a choice. He said he wanted a system that let players talk to monsters, and the idea of completing the game without killing enemies came naturally. He never considered removing the option to fight. When asked about the difficulty of playing without killing, Toby said it was central to the game's themes, encouraging players to think for themselves. He was also inspired by Moon: Remix RPG Adventure and Cave Story.
The idea of being trapped underground was inspired by the game Brandish. Toby was influenced by internet culture and comedy shows like Mr. Bean, as well as the unsettling atmosphere of EarthBound. He wanted to challenge common ideas in games. He found writing easier once he established a character's voice and mood. He believed creating the world was natural, as it reflected the stories of its characters. He wanted monsters to feel like individuals, unlike in games like Final Fantasy, where monsters are often the same.
Toriel, one of the first characters players meet, was created as a parody of tutorial guides. Toby disliked how Fi, a character in The Legend of Zelda: Skyward Sword, gave away puzzle answers too early. He also felt role-playing games lacked strong mother characters, like in Pokémon or Mother. He wanted Toriel to act like a real mother who cares about players. Initially, Toriel had to be killed to progress, but Toby changed this before the game's demo. This decision influenced his choice to let players spare monsters, showing what Undertale was about.
Papyrus and Sans are named after the fonts Papyrus and Comic Sans, and their dialogue is shown in those fonts. Both characters were inspired by J. N. Wiedle, the author of a webcomic about a skeleton named after the Helvetica font. Papyrus was originally a mean character named "Times New Roman" who wore a fedora. Sans was originally a casino owner who told puns, but Toby thought it would not be funny. This idea was later used in the Xbox One port, where Sans runs a casino. Toby said the most memorable part of making Undertale was when Papyrus rejects Frisk during their date. The scene was originally harsher but was softened after a playtester, a friend of Toby, cried during the scene.
During development, Toby found it hard to write Undyne. He tried giving her different accents and hobbies, but the only consistent detail was that she was the first boss who wanted to kill the player. Alphys was originally a man, but Toby changed her to a woman and added eyelashes to her design.
Release
Undertale's first demo was released on May 23, 2013. At that time, the demo was about 25% of the full game. It was originally planned to be released in Summer 2014. The complete game came out on September 15, 2015, for OS X and Windows, and on July 17, 2016, for Linux. The game's creator, Toby Fox, wanted to release Undertale on other platforms, but Nintendo 3DS and Wii U versions were not possible because GameMaker did not support those systems. A patch was released in January 2016 to fix bugs and add new dialogue and secrets. Sony Interactive Entertainment announced during E3 2017 that Undertale would be released for PlayStation 4 and PlayStation Vita, along with a retail version published by Fangamer. These versions were released on August 15, 2017. They included exclusive unlockable achievements and a new location called the Dog Shrine. A Nintendo Switch version was announced in March 2018, though no release date was given at the time. The Switch version highlighted a partnership between Nintendo and YoYo Games to allow GameMaker Studio 2 users to export games directly to the Switch. The Switch version was released on September 15, 2018, in Japan, and on September 18, 2018, worldwide. It included an exclusive boss fight against Mad Mew Mew. The Xbox One version was released on March 16, 2021, and featured a playable slot machine in the Dog Shrine. All console versions were developed and published by Japanese localizer 8-4 in all regions.
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 was released by Materia Collective on the same day as the game. Two official cover albums were also released: the 2015 metal/electronic album Determination by RichaadEB and Amie Waters, and the 2016 jazz album Live at Grillby's by Carlos Eiene. Another jazz duet album, Prescription for Sleep, was released in 2016 by saxophonist Norihiko Hibino and pianist Ayaki Sato. A 2x LP 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 by Nintendo for Super Smash Bros. Ultimate in September 2019, along with a new arrangement of "Megalovania." 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.
To celebrate the game's tenth anniversary, Fangamer and Toby Fox held a two-day charity marathon livestream for Doctors Without Borders. They played through a modified version of Undertale, which included new dialogue, visuals, areas, and boss fights. The livestream raised $330,000. The new fights were later released as a browser game, and the new songs and art assets were made available for download.
After Undertale's release, a small Japanese fan community formed, leading to an unofficial fan localization patch being released in early 2016. Toby Fox had planned for a Japanese translation as a future goal while working on the game. He consulted several companies and eventually chose 8-4, which had previously translated Aquaria and Shovel Knight. To ensure a consistent voice for the game, 8-4 used only one primary translator, Keiko Fuchicho, even though it delayed the Japanese version's release. She was supported by a small team of editors, proofreaders, and a programmer who 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. He continued to support and advise them throughout the process. Because PC gaming is less popular in Japan, the team also decided to release Undertale for consoles, with 8-4 handling the porting. After the localization was announced, fans were surprised by the use of the Japanese pronoun oira (おいら) for Sans, which is associated with rural life, leading to the term "oira shock." The Japanese localization was released for PS4 and Vita on August 16, 2017, and for PC on August 22, 2017.
Reception
Undertale received "universal acclaim" from critics, according to Metacritic, a website that collects game reviews. On Metacritic, it is the third-highest rated Windows game from 2015 and among the top 50 of all time. After its release, it was briefly the highest-rated PC game on Metacritic. On OpenCritic, another review site, 97% of critics recommended the game, calling it "mighty" in approval. GameSpot’s Tyler Hicks said it is "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." The game has been listed among the greatest of all time, ranking 20th in IGN’s "Top 100 Video Games of All Time" in 2021 and 34th in Dexerto’s "100 Best Games of All Time" in 2025.
Daniel Tack of Game Informer described the game’s combat system as "incredibly nuanced," noting the uniqueness of each enemy encounter. Austin Walker of Giant Bomb praised the combat’s complexity, calling it "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 noted the option to avoid combat and instead engage in friendly conversations. Jesse Singal of The Boston Globe said the game’s ability to make players empathize with monsters during non-violent actions showed "the broader, fundamental sweetness at the core" of Undertale. Gabriel Elvery of Games and Culture believed the game’s pacifist route allowed players to form parasocial interactions with monsters, which he linked to their simple, human-like portrayals, unlike the genocide route, where such interactions are impossible because monsters either flee or are killed.
Sean Travers of the Journal of Popular Culture described Undertale as a critique of the violent nature of mainstream RPGs, where players typically earn rewards by killing enemies. She noted the game’s harsh treatment of players who choose the Genocide route and ignore warnings, citing its shift in tone and disturbing imagery. Travers interpreted this as the player becoming the antagonist or a "postmodern psychopath," a character who commits immoral acts for their own reasons. She believed Undertale is innovative due to the player’s "degree of choice." Kevin Vale of Convergence compared Undertale’s handling of accountability to Night in the Woods, noting the central role of the player in both games but highlighting differences in gameplay.
Reviewers praised the game’s writing and narrative. IGN’s Plagge called the writing "strong" and "consistently funny," noting how it "built on" the game’s themes of humanity and morality. Ben "Yahtzee" Croshaw of The Escapist called Undertale the best-written game of 2015, saying it was "hilarious" and "heartfelt" by the end. Ben Davis of Destructoid praised the characters and humor, comparing the game’s tone and storytelling to Cave Story (2004). Richard Cobbett of PC Gamer said even the game’s weaker moments "just about work." Kill Screen noted that Undertale’s absurd humor was a signature feature of its creator’s style.
The game’s visuals received mixed reactions. Austin Walker of Giant Bomb called them "simple, but communicative." IGN’s Plagge said the game "isn’t always pretty" and "often ugly," but believed the music and animations made up for it. Ben "Yahtzee" Croshaw of The Escapist said the visuals "wobbled between basic and functional to just plain bad." Others praised the graphics: Daniel Tack of Game Informer said they matched the characters and settings well, and Richard Cobbett of PC Gamer noted their ability to convey emotion.
By the end of 2015, a preliminary report by Steam Spy estimated Undertale was one of the best-selling games on Steam, with 530,343 copies sold. By early February 2016, it surpassed one million sales. By July 2018, it had an estimated 3.5 million players on Steam. Japanese sales of the game on PlayStation 4 and Vita exceeded 100,000 copies by February 2018. By March 2019, it was among the ten best-selling indie games on the Switch. As of December 13, 2025, Steam Spy estimated Undertale had sold between 5 and 10 million copies on Steam.
Impact and legacy
Undertale became very popular among many people after it was released. About a year later, the game’s creator, Toby Fox, said he was surprised by how much people liked the game. He appreciated the attention but found it difficult to handle. Fox said, "I might never make a game as successful again. That’s okay with me." Ana Diaz from NPR said Undertale influenced the entertainment preferences of a whole generation and became famous through internet memes. Reid Young, the CEO of Fangamer, called the game a major success. The character Sans was especially liked by players and inspired many fan creations. Professional wrestler Kenny Omega wore a costume of Sans during a wrestling event in 2019. When Sans was added as a Mii fighter in Super Smash Bros. Ultimate, fans were happy, though some critics thought the large number of characters might reduce the game’s nostalgic value. Many fans also made their own games based on Undertale’s world, including Undertale Yellow, which took seven years to develop and was very popular when it was released in 2023.
The Undertale community has faced some problems. Some fans disagreed about the best way to play the game. After the game was released, some live streamers were criticized or harassed by fans for killing enemies or trying the "genocide" route. A YouTuber named Markiplier stopped playing the game early because he said he wasn’t enjoying it due to pressure from fans.
In July 2016, during an Internet-related meeting at the Vatican, YouTube personality MatPat gave a copy of Undertale to Pope Francis. MatPat explained his choice by connecting the game’s theme of mercy to the year 2016, which was called the Extraordinary Jubilee of Mercy. Later, in 2022, a circus group performed a song called "Megalovania" for the Pope, linking it to MatPat’s gift. Christopher Cayari from the International Journal of Education & the Arts said Undertale’s popularity shows how video game music can be useful for music teachers, as fans often share and create music related to the game.
Undertale was included in many lists of the best games of 2015. It received awards such as "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 won "Best PC Game" from Destructoid.
The game was recognized with many awards and nominations for its story, gameplay, and role-playing elements. At IGN’s Best of 2015, it won "Best Story." It was nominated for awards like "Role-Playing/Massive Multiplayer Game of the Year" and "Outstanding Achievement in Game Direction" by the Academy of Interactive Arts & Sciences. Undertale was also nominated for "Innovation Award," "Best Debut," and "Best Narrative" at the Game Developers Choice Awards. In 2016, it won the "Audience Award" at the Independent Games Festival and was nominated for "Excellence in Audio," "Excellence in Narrative," and the "Seumas McNally Grand Prize." The SXSW Gaming Awards called it the "Most Fulfilling Crowdfunded Game" and gave it the "Matthew Crump Cultural Innovation Award." At the Steam Awards, it was nominated for the "I’m not crying, there’s just something in my eye" award. In 2019, Polygon listed Undertale as one of the best games of the decade. In 2021, IGN ranked it as the 20th greatest game of all time. In Japan, a survey of over 50,000 players named Undertale the 13th greatest game of all time.
Spin-off
On October 31, 2018, Fox released the first chapter of Deltarune for free on macOS and Windows. This came after Fox had hinted at something related to Undertale the day before. Fox said Deltarune is not set in the same world as Undertale. However, some characters and settings might remind players of Undertale. The game is meant for people who have finished playing Undertale. The name Deltarune is an anagram of Undertale. Fox mentioned that Deltarune is a bigger project than Undertale. He explained that creating the first chapter of Deltarune took several years, which was much longer than making the Undertale demo. Unlike Undertale, Deltarune has only one ending, no matter what choices the player makes during the game. Chapter 2 of Deltarune was released for free on September 17, 2021. This happened after Fox formed a team to assist with further development. Once all chapters are finished, the game will be released as a complete version. Fox said he does not have a set timeline for when the game will be fully completed. Chapters 1 through 4 were sold as a paid package on June 4, 2025, and released a day later in Japan. Future chapters will be given as free updates.