FNF Toxic Sans after Undertale
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FNF Toxic Sans after Undertale


FNF Toxic Sans is a rhythm game where Boyfriend encounter masked Sans in some alternative universe after a nuclear bomb.

We all know what happens in Undertale in terms of endings, but this is a different ending, as this end occurs at the hands of human beings, and because of a nuclear bomb that led to the explosion of the world and the entry of a chemical substance to the lower bottom, which is the world of Undertale


  • Broken Bone
  • Blood Killer
  • The Last Toxic

Mod Credits:

If you had fun, make sure to check out the social media of the creators below, and follow them for more updates and other cool stuff.

this is a demo

  • Kilfor: Director/Artist/Mod owner
  • Penutbutter_Gelly: charter/composer
  • Ab_xp4: animator
  • Slendermanix2: coder
  • Korrupter: charter
  • Lionzo0: sprite artist
  • elFoxFire: Background artist
  • Get the mod for your PC here

Game Engine Credits:

  • Shadow Mario: Main Programmer
  • bbpanzu: Additional Programmer
  • RiverOaken: Main Artist/Animator
  • Also everyone that contributed on GitHub.

Original FNF Credits:

  • ninja_muffin99 – Programming
  • PhantomArcade3k and evilsk8r – ARTISTS
  • kawaisprite – TASTY MUSIC
  • AND everyone that contributed to the GitHub source.

The goal of this web optimized port is to make FNF and this mod more accessible to players that can’t otherwise play it on their potato PC, on a Chromebook,  on their Mac, on their Linux, or simply can’t run the EXE files on their computer. Also help save hard drive space. Please keep in mind that this online web port might be slightly different and/or have missing mechanics than the PC version. So make sure to also get the PC version if you have a PC.

If you want a challenge, turn off Ghost Tapping in the settings.

Recommend using Google Chrome to play FNF Mod for the best performance.

Jam to the beats and just have fun!