Undertale Yellow Routes and Endings Explained
Like UNDERTALE, Undertale Yellow changes depending on whether you kill or spare monsters. The official page promises 'three main routes'; here is what each one requires, how they differ and how to switch.
Checked against official sources: November 8, 2026
Spoiler warning: the requirements below are spoiler-light, but the "How it ends" lines reveal the final bosses and outcomes.
Undertale Yellow routes at a glance
| Route | What you do | Final boss | Endings |
|---|---|---|---|
| Pacifist | Kill no monsters at all | Ceroba | True Pacifist (spare Ceroba) or Flawed Pacifist (kill her) |
| Neutral | Kill some monsters, but don't meet the Genocide requirements | Flowey | One Neutral ending |
| Genocide (No Mercy) | Exhaust the kill counter in every area | Asgore (after confronting Flowey) | Genocide ending |
Pacifist route
Requirement: go through the whole game without killing a single monster — spare every enemy, miniboss and boss.
Good to know: unlike UNDERTALE, you do not need to finish a Neutral run first. On this route Ceroba travels with Clover through most of the Steamworks, which adds a lot of extra dialogue.
How it ends: the final boss is Ceroba Ketsukane, who wants Clover's SOUL to save her daughter Kanako. Spare her for the True Pacifist ending; kill her and you get the Flawed Pacifist ending.
Neutral route
Requirement: anything that meets neither the Pacifist nor the Genocide conditions — for example, killing a few monsters or a boss.
Good to know: the Neutral route is not treated as the "default" and has exclusive scenes. Dalv's dialogue changes with your kill count, and a Neutral-only scene plays in the Wild East saloon after you receive Starlo's letter in the Steamworks.
How it ends: there is a single Neutral ending. Flowey is the final boss; afterwards he tells Clover to "make different decisions next time" and resets your SAVE.
Genocide route (No Mercy)
Requirement: kill every monster in each area until encounters stop. Each area has a counter of 20 monsters including bosses; when it runs out, encounters say "But nobody came." Decibat and El Bailador simply disappear if you empty their area's counter before meeting them.
- You can't clear an area from one room: after 5 kills in a room in the Dark Ruins or Snowdin (3 in the Dunes or Steamworks) no more encounters spawn there until you move on.
- With 7 monsters left, the battle music becomes "Enemy Retreating" and slows down with each kill; Flowey's save-point lines tell you how many remain.
- Version 1.1 added more stock to the route's final shop; version 1.2 added a missing No Mercy check to the Steamworks (fixed in 1.2.1).
How it ends: Clover kills Starlo and Ceroba, Martlet returns transformed by a royal lab serum, Flowey is shot and Clover kills Asgore. The game closes during the credits; when reopened you are only offered RESET or STAY.
How to abort the Genocide route
You drop out of No Mercy if you reach certain story points without exhausting the kill counter, or by sparing a boss. Examples from the community wiki:
- Snowdin: apologize to Martlet repeatedly at the start of her fight until the option turns yellow, then spare her instead of depleting her HP.
- Dunes: trying to move on to Martlet's second encounter with kills left triggers a pop-up — "There are still enemies to bring justice on." — giving you the choice to turn back or continue.
- Dark Ruins: on an aborted route Dalv refuses to shake hands and skips the hangout, but stays on better terms.
Which order should I play the routes in?
There is no required order. A Pacifist run is a natural first choice: it does not need a Neutral run first, and the Neutral ending finishes by resetting your SAVE anyway. The Genocide route is the most demanding and the game treats it very differently, so save it for last if you want to see everything.
Need help on the way? Our Undertale Yellow walkthrough lists every area and boss, and the character guide explains who's who.
Routes and endings FAQ
How many endings does Undertale Yellow have?
There are three main routes. The Pacifist route ends in either the True Pacifist or the Flawed Pacifist ending depending on whether you spare or kill Ceroba; the Neutral route has a single ending; the Genocide (No Mercy) route has its own ending.
Do I need to finish the Neutral route before the Pacifist route?
No. Unlike UNDERTALE, reaching the Neutral ending is not a prerequisite for either Pacifist ending.
How many monsters do I need to kill for the Genocide route?
Every area has a kill counter of 20 monsters, bosses included. Once it is exhausted, encounters show "But nobody came." You can only exhaust 5 kills per room in the Dark Ruins and Snowdin, and 3 per room in the Dunes and Steamworks.
Which Undertale Yellow ending is canon?
The game does not say so outright, but the community wiki considers True Pacifist the most likely canon ending: at its close Clover's hat and gun float down to the garbage dump, where UNDERTALE's Bratty and Catty say they found them.