Genocide Route

For the other definition of "No Mercy Route", where all encountered monsters are killed, see Neutral Route#Leaderless Ending.

if you keep going the way you are now...
...
you're gonna have a bad time.

Sans in Snowdin

The Genocide Route leads to one of the three main endings of Undertale. It consists of the protagonist actively killing monsters, mandatory minibosses, and bosses in the underground regions.

This route's ending can occur without prior completion of the game, unlike the True Pacifist Route. Upon completion, subsequent True Pacifist Route and Genocide Route endings are altered with new dialogue and cutscenes, even after a True Reset.

On console versions of the game, the post-Genocide changes only affect the player profile used for finishing the route.

Method

Battle text after the protagonist exhausts the kill count.

Starting in the Ruins, the protagonist must repeatedly trigger the random encounters by walking in areas where encounters can occur. This is similar to level-grinding in typical RPGs, which is earning experience points before progressing. Upon fulfilling the kill counter of each area, encounters still occur, but monsters do not appear. In a font size smaller than usual, the battle text becomes, "But nobody came." This text can also appear in the Neutral Route if the kill counter has been fulfilled.

After the "But nobody came." message appears, the area's background music changes to a distorted ambient track, mus_toomuch.

After exiting the Ruins, most overworld tracks are lower in pitch and slower than their Neutral/True Pacifist Route counterparts. Some NPCs no longer appear, and slight alterations occur in some locations, such as most puzzles already being solved.

If the protagonist fails to meet the route's requirements at any point, the route reverts to the Neutral Route. This is signified by the soundtrack being unaltered, and NPCs appearing in the region where the protagonist aborted the Genocide Route. Once the Genocide Route is aborted, it cannot be returned to without reloading the SAVE before it was aborted, or resetting entirely.

Requirements

The first SAVE Point in Snowdin displays the kill counter for the first time.

The kill counter must be exhausted before approaching the boss encounter at the end of each region.

As the protagonist grinds out the kill counter for each area, the random encounters become increasingly harder to find.

After exiting the Ruins, the kill counter becomes visible at SAVE Points, which is indicated by red text.

The protagonist can also spare any number of random encounters, with exceptions listed in the below chart. Sparing certain monsters allows the protagonist to avoid monsters such as the high-defense Jerry. The protagonist can also spare certain monsters so that they can kill monsters that offer more EXP and GOLD, such as Glyde.

Once the protagonist fulfills the requirement, the SAVE Points display the message "Determination."

The following is a table of the number of random encounters, unique monsters, and bosses that the protagonist must kill:

Region	Kill #	Unique encounter	Boss	Notes
Ruins	20	-	Toriel	Napstablook does not count for the criteria, but can be fought. Alternatively, Napstablook fades away if the kill counter was exhausted beforehand. Unlike other bosses, Toriel can be fought before exhausting the kill counter, but will be fought in her Neutral Route state. Killing her contributes toward exhausting the kill counter for the Ruins.
Snowdin	16	Snowdrake Doggo Dogamy and Dogaressa Greater Dog	Papyrus	Snowdrake must be killed before the kill counter is exhausted. Lesser Dog is not required, but must be killed if encountered. Both are added to the kill counter, and are scripted to appear in at least one random encounter. It is possible to avoid Lesser Dog's by repeatedly triggering Glyde's encounters at the mysterious door. Doggo, Dogamy and Dogaressa, and Greater Dog do not count towards the kill counter, but they must be killed to fulfill the requirement. Mad Mew Mew is inaccessible.
Waterfall	18	Shyren Glad Dummy	Undyne the Undying	Undyne's transformation is triggered by selecting FIGHT against Monster Kid.
Hotland and CORE	40	Royal Guards Muffet	Mettaton NEO	So Sorry is inaccessible.
New Home	-	-	Sans	-

Excluding Napstablook, Snowdrake, and Lesser Dog, all unique monsters can be encountered after the kill counter is exhausted, which can be used to obtain extra EXP.

Failing any of the requirements aborts the route.

Differences

Ruins

Before meeting requirements

• The Vegetoid overworld encounters disappear after killing 12 monsters.
• The Froggit NPCs disappear after killing 17 monsters.
• Napstablook disappears from the six-hole puzzle room after killing 17 monsters.
  • This can be seen only if Napstablook is spared before killing 17 monsters. Unique from the other Ruins NPCs, this only takes effect upon changing rooms.

"Where are the knives."

After meeting requirements

• If the protagonist exhausts the kill counter before encountering Napstablook, they vanish when the protagonist approaches them, skipping the fight with them.

"It's me, <Name>."

• In Toriel's Home, checking the cupboard in the kitchen prompts the flavor text "Where are the knives." instead of "Inside the cupboard are cookie cutters for gingerbread monsters."
  • Inspecting the mirror displays the flavor text "It's me, <Name>." instead of "It's you!"
• When facing Toriel at the exit of the Ruins, the protagonist kills her with a single attack regardless of how well the attack is executed.
  • Upon attempting to talk to Toriel, the text "Ironically, talking does not seem like the solution to this situation." is replaced with "Not worth talking to."
• After killing Toriel, Flowey appears in the next chamber - even if he was killed on a previous Neutral Route - and identifies the protagonist as the fallen human.

Snowdin

Before meeting requirements

Sans telling the protagonist that they should continue "pretending" to be a human

• When encountering Sans, he is confused by the protagonist's lack of reaction to his joke. He then attempts to hide them behind the conveniently-shaped lamp, but they ignore him. When Papyrus arrives, he immediately leaves after Sans tells him he found a human, oblivious to the protagonist. Sans then tells the protagonist that they should continue "pretending" to be a human.
• Snowy is played at 0.4x instead of 0.95x speed.
  • It is important to note that various events cause the BGM in Snowdin to revert to its normal state (namely the word search, tile puzzle, and bridge gauntlet segments). Those occurrences do not indicate an abortion of the route.
• The SAVE Points, instead of describing that the protagonist is "filled with determination", begin counting down how many monsters the protagonist has left to kill before the route can progress (e.g. "16 left.").
• When Papyrus finally notices the protagonist, he initially fails to recognize them as a human. The BGM slows down and becomes lower in pitch when this happens.
• Doggo shivers when the protagonist approaches him.
• The protagonist can take three Snowman Pieces from the Snowman until they become a "useless pile of snow".
• On the Neutral Route, the lone snowball that is usually described as "(It looks like a snowball...) (Actually, it's a snowdecahedron.)" is instead described as "(It's a snowball.)" after the kill counter has been exhausted. On this route, this message is displayed by default.
• The protagonist ignores all of Papyrus's puzzles, and some of them appear to have been preemptively solved by Flowey.
  • The protagonist walks through the electricity maze before Papyrus finishes explaining it. The music speeds up and becomes higher in pitch after this happens.
  • Sans and Papyrus have different dialogue regarding the word search when it is either checked or skipped.
    • If the word search is skipped, Sans remarks that he should have made the puzzle a Junior Jumble, as opposed to a crossword on the Neutral Route.
    • If the word search is checked, Papyrus complains that he "CAN'T WORK IN THIS ENVIRONMENT" before leaving.
  • The switch in the snow puzzle has already been pressed down by vines.
  • The spikes are already retracted for the X --> O puzzles, and Papyrus is absent.
  • The ice bridge for the ice X --> O puzzle is already expanded.
  • The protagonist cuts off Papyrus's explanation of the tile puzzle and walks through it before Papyrus can activate it.
  • The Gauntlet of Deadly Terror is retracted after Papyrus feels that the human would not appreciate it. After Papyrus leaves, Sans warns the protagonist that they will "have a bad time" if they continue the way they are currently going, specifically mentioning the protagonist's upcoming battle with Papyrus. He then seems to teleport out of the area, and the BGM is abruptly cut off.
• If the protagonist kills Greater Dog, has yet to kill Snowdrake and the kill counter has not been exhausted, every SAVE Point reads "That comedian..." until he is killed.
  • If Snowdrake is not killed before the kill counter is exhausted, the SAVE Point text changes to "The comedian got away. Failure." and the route is aborted.

After meeting requirements

• The ball at the Ball Game disappears. Checking the hole says "There's a hole here." instead of "Ah! Wow! Woah! It's a "Hole"."
• All the Snowdin Town NPCs evacuate, except Monster Kid.
• Shop is played at 0.2x instead of 0.925x speed.
• Snowdin Town is played at 0.25x speed.
  • If mus_toomuch is triggered in Snowdin, that track plays instead.
• The protagonist can no longer sleep at the Inn.
• Inspecting the Christmas tree at the center of town displays the message "Nothing for you."
• Inspecting the unfinished book in the Snowdin Library displays the message "Some unfinished book."
• The innkeeper's child is replaced with a decoy.
• Due to QC's absence, the protagonist can steal all of her wares and 758G from the counter. Inspecting the note on the counter displays the message "Please don't hurt my family."
• Due to the Punk Hamster's absence, the protagonist can climb onto the counter at Grillby's.

Papyrus confronting the protagonist

• Papyrus tries to convince the protagonist to be a good person and immediately offers to spare them. Even after being killed, he still believes that the protagonist can do better.
  • During the confrontation with Papyrus, Bonetrousle plays at 0.2x speed.
  • Papyrus's usual Check description is replaced with "Forgettable."

Waterfall

Before meeting requirements

The smiley face appearing upon an encounter

• Starting in Waterfall, encounters are marked by a smiley face above the protagonist's head as opposed to an exclamation point.
• Like with Snowdin, most of the BGM is slowed down.
  • Waterfall is played at 0.13x speed.
  • Quiet Water is played at 0.5x instead of 0.9x speed.
  • Shop is played at 0.2x instead of 0.925x speed in Gerson's shop.
  • Temmie Village and Tem Shop are played at 0.5x speed.
• Like with Snowdin, most of the puzzles are already completed.
  • Rocks are not falling down the waterfall in the rock puzzle room.
  • The Bridge Seeds are already aligned.
  • The northern wall in the Wishing Room is already open.
• All of the NPCs are absent, except Monster Kid, Gerson, and the Temmie Shopkeeper.
  • The small bird still appears on the opposite side of the gap when the protagonist enters from the left side. However, it disappears after reaching the garbage dump.
• On the Neutral Route, most of the Echo Flowers produce a message stating "It's strangely silent." after Undyne is killed. On this route, the flowers produce this message by default.
• Due to the absence of the Ferry and the small bird, the protagonist cannot return to Snowdin or any earlier point in Waterfall until Undyne is slain.
  • All the areas between the Ferry Dock and the garbage dump also become permanently inaccessible because of this, preventing the protagonist from getting the Ballet Shoes and the Dog Residue if they have not already.
• Onionsan does not appear.
• When Monster Kid offers to help the protagonist reach the ledge, the protagonist climbs on to Monster Kid's shoulders roughly.
• The protagonist's actions upset the Mad Dummy so much that it causes them to become corporeal, turning them into the Glad Dummy. Since the protagonist helped the Mad Dummy become corporeal, they immediately offer to spare them. The dummy must be killed in order for the route to progress.
• Neither Napstablook nor the snails show up in Blook Acres, meaning that the game of Thundersnail cannot be played.
• The "Ghouliday", "Spookwave", and "Spooktune" CDs do not appear in Napstablook's home.
• Gerson remains in his shop and sells his items as usual, albeit with different dialogue. He also seems to know that the protagonist cannot harm him as shopkeepers cannot be fought, thus rendering their threats meaningless.
• Temmie Village is empty except for the Temmie Shopkeeper, who behaves normally, seemingly unaware of what is happening, and the Temmie that watches the protagonist from within the wall.
  • The Tem Shop has no option to pay for the shopkeeper's college education — this is replaced with the option to buy "Premiem" Temmie Flakes at a price of 1000G, rendering the Temmie Armor unobtainable.
• If the kill counter has not been exhausted by the time the pathway to the bridge (room_water19) is reached, a message reading "Strongly felt <number> left. Shouldn't proceed yet." appears between the second and third Echo Flowers.

After meeting requirements

• An additional, unnamed SAVE Point appears in the room before the bridge and disappears after the bridge sequence.

Undyne the Undying

• On the bridge, Monster Kid confronts the protagonist, saying that Undyne told them the protagonist had done bad things, and tells the protagonist that they began to see the truth in her words. They try to fight the protagonist; when the latter retaliates, Undyne jumps in and takes the fatal hit. Instead of dying, however, she recovers and becomes Undyne the Undying, who is significantly more difficult than the ordinary fight with Undyne.
  • During the confrontation with Monster Kid, Anticipation plays at 0.25x speed.
  • After Undyne the Undying is defeated, she dies with a smile, aware that Alphys is evacuating the monsters ahead of the protagonist and has told Asgore to absorb the SOULs he has collected.
• After killing Undyne the Undying, the "Welcome to Snowdin Town" sign disappears, although its hitbox is still present.

Hotland and CORE

Before meeting requirements

• Alphys is absent from her Lab. Instead, Mettaton acknowledges the protagonist's malice and flees.
  • The lights are already on.
  • The console that shows the protagonist says "It's me, <Name>." when interacted with.
  • Inspecting the hole in the wall displays the message "It's just here to complete the look."
  • Due to Alphys's absence, the protagonist cannot upgrade their phone to obtain the extra Dimensional Boxes.
• Like with Snowdin and Waterfall, most of the BGM is slowed down.
  • Ooo, Another Medium, Hotel, and CORE are all played at 0.5x speed.
  • Alphys does not play at all.
  • Dating Start! is played at 0.25x speed in Bratty and Catty's shop.
  • Shop is played at 0.4x instead of 0.7x speed in the MTT-Brand Burger Emporium.
• Like with Snowdin and Waterfall, most of the puzzles are deactivated.
  • Most of the lasers are off. The only exceptions are the first opposing ship puzzle to the left (as soon as the protagonist approaches the laser, it turns off automatically) and the three lasers on the conveyor belt on Floor 3 (these lasers are still active even if the puzzle in that room has been solved on the Neutral Route).
  • The puzzles involving shooting the opposing ship are already solved.
• All NPCs are absent except for the River Person.
• The Royal Guards are encountered much earlier, at the three steam vents before the entrance to Mettaton's cooking show set, and they attempt to avenge Undyne. They can both be killed in one hit. Killing them is required to continue the route.
  • Checking either of the Royal Guards during battle yields the text "I see two lovers staring over the edge of the cauldron of hell." A second Check continues the previous one's text: "Do they both wish for death? That means their love will end in hell. I couldn't stop laughing."
• Mettaton's quiz show, cooking show, news report, and musical performance do not occur.
• The elevator in Hotland can access every floor except for R3 from the start. However, Floors L1, L2, and R2 are cut off by force fields, preventing the protagonist from getting the Stained Apron and encountering So Sorry.
  • The force field that cuts off Elevator L1 disappears after reaching Elevator R3.
  • If the SAVE file is edited to enter the Art Club room, So Sorry still cannot be encountered as the sign in the Art Club room reads "(Art club is cancelled!)".
• Muffet does not show up for her bake sale. It is still possible to buy from the bake sale, but this does not prevent the fight with Muffet. Before she is fought, she does not consider the protagonist to be fit to eat but attempts to dispose of them regardless.
  • If the kill counter was exhausted in Waterfall, mus_toomuch plays in Hotland's Spider Bake Sale even if the kill counter has not yet been exhausted. The reason for this is because the track that plays at the Spider Bake Sale in other routes is Quiet Water, a track that plays in many areas throughout Waterfall along with its eponymous track, and the code that starts this theme is the same code that plays it in Waterfall.
• The Muffet fight still takes place, though the protagonist can kill her in a single attack, so long as the attack is well-executed. Killing her is required to continue the route. If not killed immediately, she has unique dialogue referencing the underground's evacuation.
  • She talks about how Alphys unsuccessfully attempted to get the spiders to evacuate.
  • The telegram she receives states that despite the protagonist being a hyper-violent murderer, they never harmed a spider since there are no other spider enemies.
• All MTT Resort NPCs except for Burgerpants are absent.
  • Due to the absence of Bratty and Catty, the protagonist can steal all of their wares, as well as 5G from their shop. A note can be found which reveals that Alphys came to evacuate them to someplace "super duper safe", but that Bratty and Catty wanted to use up their gel pens before leaving.
• Inspecting the plants in the MTT Resort reveals that "(The potted plant is judging you for your sins.)"
• A Dimensional Box appears in the lobby of the MTT Resort.
• The elevator in the CORE is functional from the start and can be used to bypass the rest of the CORE.
• The monsters that ambush the protagonist near the entrance to the CORE and before the second laser puzzle are absent, though the monsters that ambush the protagonist along the "warrior's path" are still present, even if the kill counter has already been exhausted.

After meeting requirements

• Once the Royal Guards and Muffet are killed and the kill counter has been exhausted, the route can no longer be aborted.

Mettaton NEO

• The encounter with Mettaton at the end of the CORE has the protagonist face off against Mettaton NEO. Mettaton NEO dies in a single hit regardless of how well the attack is executed, and the protagonist's LOVE is set to 19 regardless of their LV beforehand. Encounters no longer occur in any region after this.
• If the protagonist enters rooms which are not affected by the Genocide Route, such as the bridge to CORE and Alphys's lab, regular music tracks start playing again, but slowed down.

New Home

"My drawing."

• Undertale is replaced with Small Shock, which plays at 0.6x speed.
• A Dimensional Box appears in front of Asgore's Home and in the Last Corridor.
• The present box in Asgore's Home that otherwise contains the Worn Dagger now contains the Real Knife. Equipping it prompts the text "About time."
• The present box in Asgore's Home that otherwise contains the Heart Locket now contains The Locket. Equipping it prompts the text "Right where it belongs."
• Inspecting various objects throughout Asgore's Home yields unique descriptions.
  • Padlocks, first time, if no keys are used: "(He leaves them in the kitchen and the hallway.)"
  • Padlocks, otherwise: "(There are two keys.)"
  • Padlocks, while unlocking: "(I unlocked the chain.)"
  • Closet: "Our clothes."
  • Left bed: "My bed."
  • Right bed: "His bed."
  • Drawing of a golden flower: "My drawing."
  • Bookshelves/Asgore's closet: "Nothing useful."
  • Asgore's dresser: "Still has that sweater."
  • Photograph: "..."
  • Refrigerator: "No chocolate."
  • Kitchen note: "I've read this already."
  • Journal: "The entries are always the same."
  • Stovetop: "Stovetop."
  • Mirror: "It's me, <Name>."
  • Calendar: "(The date I came here.)"
• While walking through Asgore's Home, Flowey talks to the protagonist. His monologue replaces the story of Asriel and the fallen human on the Neutral Route.

Flowey's dialogue in New Home

• Unlike in other encounters and like the encounters in New Home in the Neutral Route, the fallen human's name does not appear during the encounters with Flowey.
  • Flowey tells the protagonist about his life ever since he was a flower, his own ability to SAVE, and why the protagonist started killing.
  • He seems to break the fourth wall, insulting "those sickos that stand around and WATCH it happen" for not pursuing the route themselves.
  • Flowey reiterates his "kill or be killed" mentality, saying that he and the protagonist would not hesitate to kill each other if the need arises. However, Flowey finally realizes in horror that he is not above this, and that the protagonist would eventually kill him as well if given the chance. After the protagonist appears to aggressively approach him, Flowey flees. The BGM changes to a 5x slower, low-pitched version of Anticipation when this event occurs.

Sans

• In the Last Corridor, Sans does not judge the protagonist; instead, he warns them that they will "have a bad time" should they step closer. When the protagonist ignores his warning, Sans puts up a difficult battle.
  • Sans's death automatically sets the protagonist's LV to 20.

Narration upon inspecting the red coffin within the basement

• Within the basement, inspecting the red coffin has the narrator state "It's as comfortable as it looks."

The protagonist killing Asgore

Flowey begs for his life as the route's final "enemy".

• Within the Throne Room, Asgore mentions having never seen a flower cry (referring to Flowey's attempts to warn Asgore of the protagonist). The protagonist then proceeds to attack Asgore, killing him in one hit. Flowey finishes Asgore off, and then, with his face and voice changing to Asriel's, he begs the protagonist not to kill him. Pressing any of the action buttons prompts the protagonist to kill Flowey in eight hits.

Flowey's death at the end of the route

• Instead of returning to the Throne Room, the fallen human appears on the black screen. They speak either to the protagonist or directly to the player, with no dialogue box and no voicebyte. After their introduction, a high-pitched droning noise internally referred to as mus_zzz_c will play.
  • They explain that the protagonist's "human soul" and "determination" facilitated the former's reincarnation. They claim that the player taught them the reason for their return - power - and gave them the means to gain it. It was the protagonist's SOUL and determination that allowed them and the player to "eradicate the enemy and become strong". They then list the various stats that the player increases throughout the game, describing themselves as the very feeling whenever they are increased. They offer to destroy the world so that they and the player can move on to another one. At this point, two prompts are given: "ERASE" or "DO NOT".
    • During this conversation, the player cannot use the ESC button.
    • If the player chooses "ERASE", the fallen human calls the player "a great partner" and states that they and the player will be together forever.
    • If the player chooses "DO NOT", the fallen human is initially surprised, thinking that the player must have misunderstood them. After asking "SINCE WHEN WERE YOU THE ONE IN CONTROL?", they approach the screen while laughing as a sound internally referred to as mus_zzz_c2 plays. The screen flashes red and black as this happens, and on the PC version, the game's window vibrates.
  • Regardless of which option is chosen, a slash animation then plays over a black background before the window is filled with vibrating "9"s, representing the world's destruction. The slash animation is the final point where the game can be reset without consequences: once the screen fills with 9s, the player cannot resume gameplay without accepting the fallen human's deal.
    • On the PC version, the game is forced into windowed mode and the window's name disappears during the 9s (or the jumpscare if the player chose "DO NOT"). After the slash animation, the game window shakes violently from side to side, before closing.
    • On console versions, the screen simply blacks out for 30 seconds without closing the game.

The game window shaking as the fallen human destroys the world.

Abortion

The Genocide Route is aborted if the protagonist either completes an area by sparing the boss, spares certain minibosses (e.g. Glad Dummy or Muffet) and unique enemies, or reaches certain points in the game without exhausting the kill counter. Future areas appear as though in a Neutral Route, but any previous areas remain affected by the Genocide Route attempt.

• If the route is aborted at any point before reaching New Home, the SAVE Points stop displaying the kill counter and stop displaying "Determination." once it has been exhausted, even in areas that the protagonist exhausted the kill counter in before the route was aborted, and go back to what they usually display. Exceptions to this rule are as follows:
  • After sparing Toriel.
  • After sparing Papyrus (the music in Snowdin Town remains unchanged from when the route was still in effect).
  • After sparing Glad Dummy (the SAVE Points still display the kill counter, the music is still slowed down, and encounters are still marked by a smiley face).
  • After killing Mettaton NEO without killing every monster in Hotland beforehand (similar to Glad Dummy, which means that the encounters that tell the story of Asriel and the fallen human are marked by a smiley face).
• If the route is aborted by sparing Papyrus, the protagonist may only hang out with him as they cannot flirt with him during the battle. Sans is at his post in Waterfall, thanking the protagonist. Sans does not offer to take the protagonist to Grillby's, as Snowdin is already evacuated.
• If the route is aborted after reaching Waterfall, encounters stop being marked by a smiley face and go back to being marked by an exclamation point.
• If the Genocide Route is aborted by sparing Monster Kid, the protagonist fights Undyne normally.
• There is a specific Neutral Route ending that can only be reached by fighting Mettaton NEO without having killed every monster in Hotland/the CORE beforehand. Mettaton still dies in a single hit, though the damage he takes is significantly lower and does not set the protagonist's LOVE to 19. He tells the protagonist that they were "HOLDING BACK", exploding after his speech. In the ending's phone call, Sans hands the phone to Alphys.
  • If the route is aborted by sparing Muffet or the Royal Guards before facing Mettaton, the protagonist enters the Neutral Route. However, NPCs in Hotland still do not appear, including Muffet and the Royal Guards themselves after being spared. This also leads to Alphys's ending.
• If the route is aborted and Flowey is spared, Flowey chastises the player for aborting the route before asserting that they just wanted to see what peace was like before taking it all away.
  • If the player resets after leaving the Ruins and before the world's destruction, Flowey confronts the protagonist at the beginning of the Ruins and wonders why they had reset before telling them to do whatever they want.

If the protagonist has gone past the point of no return in the Genocide Route (killing the last monster in Hotland/the CORE before the Mettaton NEO fight), they can simply reset their game as long as they do not give an answer to the final question from the fallen human.

Post-Genocide game

The fallen human speaks without a dialogue box in the abyss.

Upon rebooting the game, the player is met with a black screen and howling wind. The game's window has no name, and inputs do nothing. The player must wait for 10 minutes before the fallen human addresses them. On console versions, there is only a black screen after the world is destroyed and howling wind is heard after 30 seconds have passed, after which the player must wait for 10 minutes as normal.

The fallen human reminds the player that they destroyed the world and then questions if the player thinks they are above consequences.

• If the player selects "YES", they simply say, "Exactly."
• If the player selects "NO", they ask, "Then what are you looking for?"

However, they suggest that they could reach a compromise, and offers to restore the world in exchange for the protagonist's SOUL. If the player agrees, the game closes and appears to load normally the next time it is opened, while the console versions immediately reset. If the player declines, the fallen human leaves the player in the abyss. Rebooting the game and waiting for another 10 minutes will cause them to reappear with the same offer.

Once the offer is accepted, the game closes. When re-opened, the game functions almost as if a True Reset has been performed, with even Flowey having no memory of previous playthroughs. All future True Pacifist and Genocide endings are altered, but Neutral Route endings remain unchanged. The player fights Omega Flowey on the next Neutral Route.

Changes

The True Pacifist Route's ending is noticeably altered.

• At the end of a post-Genocide True Pacifist Route, the following occurs:
  • If Frisk chooses to stay with Toriel, they turn over in bed during the final scene and face the camera to reveal the fallen human in place of Frisk. A lower-pitched version of Omega Flowey's laugh plays after the screen cuts to black.
  • If Frisk says they "have places to go", the photograph of Frisk and friends shown in the final scene changes — Frisk is replaced with the fallen human, and the faces of all the other characters have been crossed out with a red X. "The End" text changes from white to red, and the Annoying Dog does not show up to sleep under the text. An extremely slowed-down version of Anticipation plays three seconds after the "THE END" text appears.
• At the end of another Genocide Route, the following occurs:
  • The fallen human calls themselves "The demon that comes when people call its name." Time after time, they will appear, and with the player's help, they will eradicate the enemy and become strong. However, they note that they and the player are not the same, stating that the protagonist's SOUL has feelings they no longer understand. They wonder why the player continues to recreate the world, and why they continue to destroy it. They conclude that the player is "wracked with a perverted sentimentality", and suggests that should they recreate the world once again, a different course of action would be advised.
  • If the player selects "DO NOT" this time, the fallen human points out that this very feeling is what they had been talking about. They then comment that "YOU MADE YOUR CHOICE LONG AGO", followed by the same jumpscare and the game's abrupt closure that occur upon completing the route for the first time.
  • As the fallen human already has the protagonist's SOUL and is fully aware of the previous events, any future Genocide Route endings will reuse the same dialogue, and instead of making another offer, the world is automatically reset regardless of the choice.
  • On console versions, after the world is destroyed again, the game does not close. Instead, the screen blacks out for roughly 30 seconds before the regular title screen plays again.

Consequence avoidance

The first two sub-sections only apply to the computer versions and the third only applies to the console versions.

Save locations

Default save locations are as follows:

• Linux:
  • DRM-free (pre-1.02): ~/.config/UNDERTALE_linux
  • Steam (pre-1.02): ~/.config/UNDERTALE_linux_steamver
  • 1.02 and later: ~/.config/UNDERTALE
• macOS: ~/Library/Application Support/com.tobyfox.undertale/
• Windows:
  • Windows XP: %SystemDrive%/Documents and Settings/%USERNAME%/Local Settings/Application Data/UNDERTALE
  • Windows Vista and later: %LOCALAPPDATA%/UNDERTALE

Modifying/deleting files

To return to a playable state, the player can enter their save data folder and either:

• Delete the last directory in the aforementioned save location for the player's respective system; this removes everything the player has done in the game as if it is being played for the first time.
• Delete or rename the files system_information_962 and system_information_963 in the aforementioned save location. This removes any effects of having done the Genocide Route. The system_information_962 file is created after erasing the world, and system_information_963 is created after the player gives the protagonist's SOUL to the fallen human.
• Uninstall the game and do a fresh reinstall.

GOG players using GOG Galaxy may need to disable cloud saving before carrying out any of these steps. Also, these methods are not sufficient for players of the Steam version, as the Steam Cloud backs up the acquisition of the system_information_962 and restores it if deleted (even if cloud synchronization is disabled). Players of the Steam version have to wait 10 minutes and accept the offer, changing system_information_962 to system_information_963. This deletes system_information_962 from Steam Cloud and does not upload anything. Players can delete system_information_963 in the save location later. There is also a way to render the system_information files unreadable by Undertale by modifying their security settings under file properties to deny read permission.

Console versions

On console versions, the consequences of the Genocide Route can be removed if the player simply deletes the Undertale save data from the console's storage or by deleting their player profile data of Undertale.

Demo

After completing a Genocide playthrough in the Undertale Demo, the ending screen appears with red text that reads "That was fun. Let's finish the job." replacing the credits while playing Anticipation at a very slow speed. Also, all the pages of the manual but the first and last are replaced with said ending screen, and the last page is replaced with a picture of a faceless Flowey.

• 
  The faceless Flowey.
• 
  The ending screen.

Trivia

• The flavor text "But nobody came." is a reoccurring line in Undertale:
  • The line appears as an encounter flavor text when the kill counter for any area is exhausted, even if the player is not pursuing the Genocide Route.
  • In the room with the last Echo Flowers, when crossing through all the flowers but then backtracked to the second flower before leaving the room, where after "Toriel" finishes speaking, Flowey says the line. This can only happen on a playthrough Toriel was previously killed on.
  • The line randomly appears as a neutral flavor text in Memoryhead's encounter.
  • The line appears in Lemon Bread's encounter, including many ACTs such as Call or one of her neutral quotes.
  • The line appears when entering the Snowdin shop and Bratty and Catty's shop during the Genocide Route.
  • Flowey says this line twice during his monologues: once as Omega Flowey in the Neutral Route, and at New Home near the end of the Genocide Route.
    • The flavor text may have originated from EarthBound; when an enemy calls for help during battle but no reinforcements show up, the text "But nobody came." is used.
• The Ruins is the only area that has neither altered BGM (except for Toriel's Home containing Empty House) nor solved puzzles, as it is the first area of the game and no criteria for the Genocide Route are met until the kill counter for the Ruins is exhausted.
• In addition of being unkillable, Napstablook is specially programmed not to increase the kill counter. They are the only enemy outside of Snowdin with this distinction.
• In version 1.00, the Snowdin SAVE Point message "That comedian..." appeared even if Snowdrake was already killed. According to Toby Fox, the message's frequency was a bug and was fixed in version 1.001.
• Before Undyne the Undying disintegrates, she states that Alphys will instruct Asgore to absorb the six human SOULs if Undyne fails to defeat the protagonist. When the protagonist encounters Asgore, he has not.
• The Royal Guards' Check text is a direct reference to the Japanese novel Kitchen by Banana Yoshimoto.
• If the route is aborted by sparing Muffet or the Royal Guards after the kill counter for Hotland has already been exhausted, fighting Mettaton NEO still sets the protagonist's LV to 19.
• Since Mettaton NEO does not attack during the fight with him and Alphys does not meet the protagonist directly during this route, yellow mode is not seen. This is shared with the Nintendo Switch-exclusive SOUL mode of Mad Mew Mew.
• Sans's last words after the fight with him include "don't say i didn't warn you", possibly indicating that he knew what would happen at the end of the route.
• On console versions of the game, the dynamic borders are immediately disabled upon engaging Asgore.
• There is unused code for the game deleting all of its files immediately after the fallen human destroys the world.
• While Toriel is the only boss who can be killed as part of the area kill counter, Undyne also contributes toward it. This can be seen by failing to exhaust Waterfall's kill counter on a Genocide Route, killing Undyne, then backtracking to an earlier SAVE Point to compare the kills remaining. If Undyne was the last kill required to exhaust the kill counter, "But nobody came." encounters also occur, though the Genocide Route remains aborted.
  • Mettaton EX contributes as well, though as this form cannot be encountered while the kill tracker is active, the only way to view this is by killing 39 monsters in Hotland or the CORE, then killing Mettaton as the 40th, triggering the "But nobody came." encounters. Mettaton NEO avoids this by not being tracked as a kill unless all other Genocide Route requirements are met.