A downloadable game for Windows

This is Undertale Customs, a fangame series where you face off against monsters, and have the choice to either spare them or kill them.

Current Version (1.3.0)
Please check the included readme file in the game folder. If the current version of your game is outdated, download the current version on this website or on gamejolt, and replace the files previously downloaded with the ones you have just downloaded, in order to get the latest content for Undertale Customs.

Please check out my Gamejolt page for news on Undertale Customs:

Install instructions

Open the included ZIP file and click on the executable to start the game, or drag the files to a folder on your computer, then click on the executable to start the game. If you already have a previous version of the game saved to your computer, delete the contents of the previous version, and copy the contents of the new version to your computer. You may want to read the included readme file as well.


Undertale_Customs.zip 30 MB


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Played through it and absolutely loved the first chapter! 

is it possible to make it compatible with mac?

awesome! its like undertale, BUT better!


I had a total blast playing this game, the atmosphere this creates is exactly the same as the first game! The character, the battles! Oh i feel like I am playing undertale again for the first time! This game was a great experience from start to finish and I cant wait for the other episodes! 

your late for class!!!

This is cool

Hi Mystreyracer 2nd react Of Your Game Its Awesome 100000000000000000000000000000000000000/10 I Like it Make The Story Mode Fast Plsssssssssss

i love it

dis is a little funny  its very fun to play tho!


Uh totes great( coming from a 9 year old

awsome(but not good as the real one)


if you will like to do well you can play the rele one :)

if you will like to do well you can play the rele one :)

Where is the engine? How is it going?

Can you please make this compatible for Apple too? You would make some one i know very happy, and she is not letting me buy her Undertale... .

Hey man,you'r game is just THE MOST COOL GAME I PLAYED OF MY WEEK !!!Oh,and i can't wait the part 3 ! Im very noob on your game ^_^

This is an awesome game! i cant wait for part 3 to come out

I wonder If there is Pizza Involved


Awsome game

Thanks :P

so with customs, can we add monsters?

I'm leaving the engine closed source, as I'm going to eventually be using it commercially for my own projects, so most likely no.


I HAVE DESTROYED THE MONSTER THAT YOU HAVE CREATED AT https://www.youtube.com/watch?v=7dhFGShEdjg!!!


I followed you, and I AM SO PROUD OF MYSELF

Good :P

how long is this game

2 Episodes right now. Story mode will have 5 bosses, and a final boss for each path.


Played the game (soon I post letsplay) and it's amazing! Can't wait for more customs and also the story mode!!!

Thanks! :P I have the next 3 episodes planned, and the story mode, after I finish Undertale Yellow :P

That's awesome! So Yellow is yours too and you are still working on it!! Great! So glad =)

I'm sooo baad at this!

Good job at duplicating that feel though!

First Playthrough! Thanks! :D

Hey, so I have some questions to ask, if you don't mind, to improve the game:

1.Is the framerate dipping down at all in the game? I've gotten some feedback about the framerate, and tried to reduce it, then tested it on a potato, with no noticeable lag.

2. How difficult was the fight? I'm probably gonna be adding in a patch to add warning signals of where the projectiles are gonna go in the future.

Thanks for the feedback though, always appreciated :P

I also updated the game with Episode 2, so if you wanna try that out, you can as well :D

For me, the framrate didnt drop at all during the game. However, i cant beat Mettaton Ex! I am awful though, so it may be that. But lol, if you see this, can you make episode 3? heh, its been a year