---
title: "Undertale: Complete Guide"
game: "Undertale"
game_url: "https://qna.gg/games/undertale"
author: "Qloud"
author_url: "https://qna.gg/players/Qloud"
topics: ["Bosses", "Walkthroughs", "Secrets", "Endings"]
summary: "A route-by-route guide to Undertale: how the battle system works, how to get the Neutral, True Pacifist and Genocide endings, boss tips for every major fight, and the secrets people usually miss. Researched September…"
url: "https://qna.gg/g/undertale-complete-guide-d1bc7e49"
published: "2026-09-27T16:34:45.588Z"
updated: "2026-09-27T16:34:45.588Z"
source: "QnA.GG"
---

# Undertale: Complete Guide

A route-by-route guide to Undertale: how the battle system works, how to get the Neutral, True Pacifist and Genocide endings, boss tips for every major fight, and the secrets people usually miss.

*Researched September 2026 — current as of PC version 1.08 (December 2017; the game has been stable since). Live games change; check the linked sources if something differs.*

> Spoiler warning: this guide names bosses and ending requirements.

## Quick Start

1. **You never have to kill anyone.** Every enemy can be spared by using ACT until their name turns yellow, then choosing MERCY, then Spare.
2. **Play blind first if you can.** Undertale's best moments rely on surprise. Come back to this guide when stuck.
3. **Your first ending is a Neutral ending.** True Pacifist requires finishing a Neutral run with zero kills, then reloading your save.
4. **The game remembers.** Resetting or reloading doesn't erase everything - characters comment on what you did in earlier attempts.
5. **Blue attacks: stand still. Orange attacks: keep moving.** This rule saves a lot of HP.
6. **Save at every star.** Save points also fully heal you.
7. **Carry healing items.** Buy cheap consumables in each town; Snowdin and Hotland shops are the main stops.
8. **Controls:** Z (or Enter) confirms, X (or Shift) cancels, C (or Ctrl) opens the menu, arrow keys move. F4 toggles fullscreen; hold Esc to quit.
9. **There are no Steam achievements** for Undertale - completion is about endings, dog counting, and secrets.

## How Battles Work

Each turn you choose from four buttons:

| Button | What it does |
|---|---|
| FIGHT | A timing bar: stop the moving line near the center for more damage |
| ACT | Talk, compliment, check, flirt and other enemy-specific actions |
| ITEM | Use healing or equipment items |
| MERCY | Spare (when the enemy is ready) or Flee |

Then the enemy attacks, and you control your SOUL (a heart) inside a box, dodging bullets like a shoot-'em-up.

### SOUL modes

| Color | How it works | Seen in |
|---|---|---|
| Red | Free movement (default) | Most fights |
| Blue | Gravity - jump with Up | Papyrus, Sans |
| Green | Can't move; block with a shield facing a direction | Undyne |
| Purple | Move between web lines | Muffet |
| Yellow | Shoot upward with Z | Mettaton |

### Stats

- **LV (LOVE) and EXP** go up only when you kill. At LV 1 you're weaker but defense and attack items make up for it.
- **HP** rises with LV, so pacifist runs rely more on items and dodging skill.
- **Check** enemies with ACT - it shows their stats and a hint about how to spare them.

## Routes and Endings

| Route | How | Outcome |
|---|---|---|
| Neutral | Anything that isn't True Pacifist or Genocide | One of many variations based on who you killed/spared |
| True Pacifist | Neutral with no kills, then befriend Papyrus, Undyne, Alphys, then the True Lab | The "real" happy ending and full story |
| Genocide | Kill every monster in each area until encounters run out | A dark, harder route with unique bosses |

### True Pacifist requirements

1. **Finish a Neutral run without gaining any EXP.** Sparing Flowey at the end is recommended - he gives you hints about what to do next - but killing him grants no EXP and doesn't fail the route.
2. **Reload your save** (you'll be before the final area).
3. **Papyrus's hangout** in Snowdin (spare him and go on his date).
4. **Undyne's hangout** at her house in Waterfall - you need to spare her in Hotland first by giving her water from the water cooler when she collapses.
5. **Deliver Undyne's Letter to Alphys**, then **Alphys's date** at the garbage dump.
6. **Return to Alphys's Lab when Papyrus calls** - follow Alphys's note to the "bathroom" door; the elevator behind it takes you to the **True Lab**. Explore it fully.
7. **Face the final boss** and use the SAVE mechanic to reach your friends.

**What doesn't break the route:** attacking without killing, killing the Dummy in the Ruins, and the Asgore/Flowey outcomes at the end of Neutral (none grant EXP). Attacking Mad Mew Mew when she can be spared also doesn't abort it, though sparing her is the nicer outcome.

### Genocide requirements

- In each area, keep fighting random encounters and killing everything until the game says "But nobody came."
- Check the kill counter by opening a save point - if it shows a number, you haven't cleared the area.
- Missing a single required kill quietly drops you onto a Neutral route.
- Genocide unlocks unique encounters, including one of the most notorious boss fights in indie games.
- **Genocide permanently affects future True Pacifist endings** in that install. Think carefully before doing it.

## Area Walkthrough and Boss Tips

### The Ruins

- **Flowey** introduces the "friendliness pellets." Don't touch them.
- **Napstablook:** keep using Cheer until they leave happily.
- **Toriel:** keep choosing Spare repeatedly - it seems to do nothing, but after several turns the fight ends peacefully. Her attacks avoid you if your HP is low.
- **Items:** Toy Knife and Faded Ribbon are in the Ruins; the Spider Bake Sale sells the Spider Donut and Spider Cider (buying something helps against Muffet later).
- Answer Toriel's pie question however you like; it only changes flavor.

### Snowdin

- **The dogs:** Doggo (don't move when he's looking), Lesser Dog (pet repeatedly), Dogamy and Dogaressa (roll around, then pet), Greater Dog (call it, then pet and play).
- **Papyrus:** use Spare or Flirt; survive his blue attacks by standing still, and his gravity phase by jumping. At the end, he offers his friendship.
- **Shop:** buy the **Tough Glove** and **Manly Bandanna** if you're not pacifist, or healing items for a pacifist run.
- **Sans** appears throughout; his phone number and later interactions matter for some Neutral endings.

### Waterfall

- **Shyren:** hum and help her sing.
- **Mad Dummy:** stand so its knife and missiles hit the dummy itself.
- **Undyne** chases you through Waterfall. In the fight, the green SOUL shield blocks arrows; later, **flee downward** to escape into Hotland.
- **Temmie Village:** buy Temmie Flakes and the **Temmie Armor** (expensive, but price drops the more you die). You can also pay for Temmie's college.
- **Ballet Shoes**, **Old Tutu** and **Cloudy Glasses** are all found in Waterfall.

### Hotland and the CORE

- **Alphys and Mettaton** drive most of Hotland's story beats: the quiz show, cooking show, news report and puzzles.
- **Royal Guards 01 and 02:** use their ACT options (such as Clean Armor and Whisper) until they open up to each other - then they walk off.
- **Muffet:** buying from the Spider Bake Sale makes the fight easier; you can also pay her off. Her pet spider phase moves the web; keep to a lane and time jumps between lines.
- **Mettaton EX:** use Pose, Boast, Heal on camera and dodging well to push the ratings up. At 10,000 ratings he ends the show early.
- **Bratty and Catty** sell the **Empty Gun**; the **Burnt Pan** and **Stained Apron** are also in Hotland.
- The CORE is a maze; follow the signage and use save points.

### New Home

- Read the dialogue in Asgore's home; it tells the full backstory.
- **Worn Dagger** and **Heart Locket** are found here - the strongest normal gear.
- **Asgore:** you can't spare him directly; defeat him. On a Neutral route, Flowey intervenes.
- **Omega Flowey (Photoshop Flowey):** dodge through each phase and use ACT when prompted to call for help - the human SOULs assist you. Saves happen automatically during the fight, so a death isn't a full restart.

## Gear Summary

| Weapon | Where (rough) | Armor | Where (rough) |
|---|---|---|---|
| Stick | Start | Bandage | Start (Ruins) |
| Toy Knife | Ruins | Faded Ribbon | Ruins |
| Tough Glove | Snowdin shop | Manly Bandanna | Snowdin shop |
| Ballet Shoes | Waterfall | Old Tutu | Waterfall |
| Torn Notebook | Waterfall | Cloudy Glasses | Waterfall |
| Burnt Pan | Hotland | Stained Apron | Hotland |
| Empty Gun | Hotland (Bratty and Catty) | Cowboy Hat | Hotland |
| Worn Dagger | New Home | Heart Locket | New Home |
| Real Knife | Genocide only | The Locket | Genocide only |

Temmie Armor (Temmie Village) is the strongest armor you can buy in a non-Genocide run.

## Secrets and Missables

- **Dog Shrine:** donate gold in Waterfall to upgrade a small shrine.
- **The Mysterious Door** and the **Gaster Followers** appear only with certain "fun" values - randomized and rare.
- **Hard Mode:** name yourself "Frisk" at the naming screen.
- **Some names trigger special responses** at the naming screen.
- **Nice Cream** in Snowdin and Waterfall comes with punch cards you can redeem.
- **The entries and tapes in the True Lab** are key lore - read and watch everything on True Pacifist.
- **Toriel's phone calls** in the Ruins change based on your actions.
- **Sans and Grillby's:** talk to Sans in Snowdin and take him up on his offers - his dialogue changes across routes.

## Common Mistakes to Avoid

1. **Killing a single monster "by accident" on a pacifist run.** One kill locks True Pacifist until you replay. Use the Check ACT to learn how to spare.
2. **Not sparing Flowey at the end of Neutral.** It isn't strictly required, but sparing him gets you his hints about how to reach True Pacifist.
3. **Skipping Undyne's water in Hotland.** Without it, you can't get her hangout.
4. **Leaving the True Lab early.** Explore it all to finish the story.
5. **Moving during blue attacks.** Stand still and they pass through.
6. **Doing Genocide casually.** It changes your future True Pacifist ending in that install.

## Advanced Tips

- **Crit timing:** stopping the FIGHT bar exactly in the center gives bonus damage - useful on Neutral runs.
- **Use items mid-fight wisely:** healing items take a turn; the Butterscotch Pie from Toriel fully heals.
- **Defense matters on pacifist runs:** Temmie Armor, Cloudy Glasses and Heart Locket help with invincibility frames and damage reduction.
- **Mettaton EX:** save your best dodges for the camera-heavy phases, and use items when it says "heal" for bonus ratings.
- **Genocide Sans:** learn the attack patterns in order; the fight is pure memorization, so stock your best healing items and expect many attempts.
- **Undoing Genocide** means manually deleting the game's save and system files (with Steam Cloud turned off so they don't come back). Treat it as a one-way choice.

## FAQ

**How long is Undertale?**
Roughly 6-7 hours for a first Neutral run; True Pacifist adds a couple more hours.

**Can I get True Pacifist on my first run?**
No. You must finish a Neutral route first, then reload your save to unlock the final steps.

**Does killing Toriel or Papyrus ruin my run?**
It locks you out of True Pacifist for that playthrough, but you still get a Neutral ending.

**Is Genocide worth doing?**
Many players prefer to watch it online. It's intentionally uncomfortable and permanently changes future Pacifist endings.

**How many dogs are there?**
The store page joke asks you to count. The main dog encounters include the Annoying Dog, Doggo, Lesser Dog, Greater Dog, and Dogamy and Dogaressa - plus the Dog Shrine and many dog cameos.

**Is Deltarune a sequel?**
Deltarune is a separate game by Toby Fox set in a different world with familiar characters. Undertale stands alone.

**The game won't launch after a Steam client update - what now?**
The developer's 2016 note recommends opting out of the Steam client beta; you can also switch Undertale to the `old_version_100` beta branch in Properties if the latest version misbehaves.

## Sources

- [Undertale on Steam](https://store.steampowered.com/app/391540/)
- [Steam news: UNDERTALE Updated / Steam Client Beta Issues](https://store.steampowered.com/news/app/391540)
- [Undertale Wiki - True Pacifist Route](https://undertale.wiki/w/True_Pacifist_Route)
- [Undertale Wiki - Version history](https://undertale.wiki/w/Version_history)