Undertale Yellow - Play Online Free in Your Browser

What is Undertale Yellow?

Undertale Yellow is a full-length fan game set before the events of Toby Fox's UNDERTALE. You play as Clover, a cowboy-hatted kid who climbs Mount Ebott to find out why five humans have gone missing, and falls into the Underground with a talking flower named Flowey as a travel companion.

* Five humans, missing...

* In this full-length followup to the friendly RPG where nobody has to die, you decide how every encounter plays out.

— official Game Jolt description

It was made by Team Undertale Yellow, a volunteer group led by director MasterSwordRemix that grew to more than twenty people over almost eight years of development. The game was built in GameMaker Studio and released for Windows on December 9, 2023. Wikipedia reports about 350,000 downloads in its first month, and on Game Jolt it has over 73,000 followers.

Like the original, Undertale Yellow mixes exploration, puzzles and bullet-hell battles where you can fight or spare every monster. It adds brand-new areas the original never showed — the Dark Ruins, the desert Dunes, the cowboy town of the Wild East and the old power plant called the Steamworks — along with dozens of new characters and more than 100 music tracks.

How to play Undertale Yellow in your browser

Press Play Undertale Yellow. The first launch downloads roughly 180 MB of game data; a loading bar shows progress. Music tracks stream in as each area needs them.
Click inside the game once so it receives your keyboard. On first launch a disclaimer explains that the game is fan-made; press Z or Enter to continue.
Pick a difficulty when you start a New Game (added in version 1.3) and watch the opening story.
Walk up to the glowing yellow save stars to SAVE. Your file is stored in this browser, so you can close the tab and continue later.
Use Fullscreen under the player for a bigger view. The game keeps its original 4:3 picture.

Undertale Yellow controls

↑↓←→
Move, steer your SOUL

Z / Enter
Confirm, talk, shoot

X
Cancel, skip text

C
Open the menu

The C-key menu is confirmed in the official 1.3 patch notes; the game also has a dedicated run button and full support for XInput gamepads on the official Windows build. On phones and tablets the browser version shows touch buttons for the arrows, Z, X and Enter.

Undertale Yellow screenshots

Official screenshots from Team Undertale Yellow's Game Jolt page, cropped to the game's native 4:3 frame.

Clover in a corridor of the Dark Ruins, the purple lower layer of the Ruins — Dark Ruins

Undertale Yellow battle against Crispy Scroll with FIGHT, ACT, ITEM and MERCY buttons — Battle: Crispy Scroll

Clover walking through the snowy paths of Snowdin with a save star — Snowdin forest

A cabin in Snowdin with a monster resting outside in the snow — Snowdin cabin

Clover walking down a rope-lined path in the desert Dunes — The Dunes

Battle screen: Insomnitot staggers forward, Clover at LV 1 with 20 HP — Battle: Insomnitot

Clover standing between two monsters outside a building in the Wild East — Wild East

Clover on a broken stone ledge in the Dark Ruins — Dark Ruins ledge

Battles: a SOUL that shoots back

Battles work like UNDERTALE: on your turn choose FIGHT, ACT, ITEM or MERCY, then dodge the monster's bullet patterns inside the box. Two things are different:

The attack target is a circle. A white ring shrinks toward the centre; press Z as it gets close to the middle for more damage. Let it reach the centre and you miss.
Your yellow SOUL can shoot. Clover's weapon is a toy gun, and in some fights the yellow SOUL fires back at attacks instead of only dodging. An Auto-Fire option eases hand strain.
Bosses change the rules. Wikipedia notes that sheriff Starlo ties up your SOUL in his first phase, restricting your movement; other bosses use rhythm or chase mechanics.

Sparing works as you'd expect from UNDERTALE: ACT until the monster's name turns yellow, then use MERCY. How many monsters you kill decides your route — read Undertale Yellow routes and endings before you commit.

Undertale Yellow features

Dodge bullet patterns and decide every monster's fate in a classic UNDERTALE-style RPG.
Dozens of brand-new characters, from Royal Guard recruit Martlet to the Wild East sheriff Starlo.
Three main routes — Pacifist, Neutral and Genocide — each leading to a different ending.
135 music tracks: new themes plus remixes of UNDERTALE favourites, free to download from Game Jolt.
New areas of the Underground with their own history, puzzles and secrets.
A run button, and letters from past pals delivered through the UGPS mail system.
SAVE and RESET with "a familiar travel companion" — Flowey.

The story so far (spoiler-free)

Long ago, humans and monsters went to war. The monsters lost and were sealed underground by a barrier that only seven human SOULs can break. Years later, humans who climbed Mount Ebott keep disappearing. With a missing poster in hand, Clover heads up the mountain to investigate — and jumps into the Underground on purpose.

Undertale Yellow opening: five coffins with heart symbols, 'A spell that could only be broken with seven human SOULs.' — Opening: the human SOULs (captured in the browser version)

Undertale Yellow opening: Mount Ebott at sunset, 'Few humans have braved this mountain.' — Opening: Mount Ebott (captured in the browser version)

Undertale Yellow opening: Clover holding a MISSING poster on the path up the mountain — Opening: the missing poster (captured in the browser version)

From there, Clover meets a new cast of monsters on the long way toward New Home. Our Undertale Yellow guide walks through each area in order.

Accessibility and difficulty options

Difficulty select when starting a New Game (version 1.3).
Easy Mode: hats give DEF so you take less damage; can be changed mid-playthrough (version 1.1).
Auto-Fire to reduce hand strain; since 1.1 it can be toggled from the death screen of relevant fights.
Auto-Rhythm plays the notes for you in the rhythm boss fight as long as you are in the right lane.
No Screenshake when you take damage.

Version history

Feb 2016Development starts after Toby Fox replies "Do what thou wilt." The Game Jolt page goes up on March 28, 2016.
Nov 30, 2016First public demo released.
Mar 5, 2023Planned winter 2022 release slips: the team says its endgame ambitions "ballooned".
Dec 9, 2023Full game released free on Game Jolt.
Dec 14, 2023Version 1.1: Easy Mode and Auto-Rhythm options, a reworked final Pacifist boss and dozens of crash and softlock fixes.
Jul 13, 2025Version 1.2: typo fixes, an attempted fix for the final Pacifist cutscene slowdown and a missing No Mercy check in the Steamworks (1.2.1 and 1.2.2 followed).
Jul 30, 2026Version 1.3: remade sprites, difficulty select on New Game, guaranteed flee after 2 failed attempts and about 30% more G from enemies.
Aug 2026Hotfix 1.3.1 — the version you play on this page.

Full patch notes and file sizes are on the Undertale Yellow download page.

What critics said

Rock Paper Shotgun (Dominic Tarason) called it his "favourite unfinished fan-game" before release.
PCGamesN (Will Nelson) recommended it to UNDERTALE fans and called it "nothing short of astounding" that another group brought the series "full circle".
RPGFan (Aleks Franiczek) wrote that in some respects the game "even surpasses" UNDERTALE.

Quotes as collected by Wikipedia's Undertale Yellow article. On Game Jolt, about 98% of more than 8,700 player ratings are positive.

Quick facts

Developer: Team Undertale Yellow (director: MasterSwordRemix)
Release: December 9, 2023 · free
Current version: 1.3.1
Engine: GameMaker Studio
Official platform: Windows (Game Jolt, IndieDB)
Genre: RPG, bullet hell, fan game
Native resolution: 640 × 480 (4:3)
Soundtrack: 135 tracks

Undertale Yellow FAQ

Can I play Undertale Yellow online?

Yes. Press Play on this page to run Undertale Yellow in your browser. This is an unofficial web port of the official Windows files (version 1.3.1); the official release is the free Windows download on Team Undertale Yellow's Game Jolt page.

Is Undertale Yellow free?

Yes. Undertale Yellow is a free fan game. Team Undertale Yellow released it on Game Jolt on December 9, 2023 and never charged for it; the team says Game Jolt and IndieDB are the only places it hosts the official download.

Is Undertale Yellow official?

No. It is a fan-made prequel to UNDERTALE. UNDERTALE belongs to Toby Fox. According to the team's own FAQ, they emailed Toby Fox before development began asking if they could make a fangame, and he replied "Do what thou wilt."

Do I need to play Undertale first?

You can start with Undertale Yellow, but the team recommends it for veterans of UNDERTALE: the official page warns that it contains some spoilers for the original game and a slightly higher difficulty.

How long is Undertale Yellow?

The team does not publish an official play time. It is a full-length game with three main routes (Pacifist, Neutral and Genocide), so seeing everything means several playthroughs.

Does my progress save in the browser?

Yes. When you SAVE at a save point, the browser version stores the save file in your browser's storage for this site. We tested closing and reopening the page and the save was still there. Clearing site data, using private browsing or switching browsers will lose it.

Can I play Undertale Yellow on a phone or tablet?

The browser version shows on-screen arrow keys plus Z, X and Enter buttons on touch screens, and we were able to move Clover and advance dialogue in phone testing. It downloads about 180 MB before the title screen, so use Wi-Fi. A keyboard is still the most comfortable way to play.

Is there a Mac version of Undertale Yellow?

Not an official one. The team's FAQ says plans for a Mac port fell through because the process was expensive and tedious. The browser version on this page runs on Macs in a modern browser.

Official pages and sources

Facts on this page come from the developers' Game Jolt page and patch notes, plus Wikipedia and our own testing of the browser version. Please support the team by following them on Game Jolt.