If you're looking to hack yourself more gold or change your game's difficulty, or explore hidden secrets, you'll need to know where the Undertale game files are. This article will teach you how to get into your game files and modify them safely.
There are many tools and mods available online to modify Undertale's game files. Some of these tools are a little unstable or may cause glitches and errors. Before you experiment with these mods, make sure that you have a backup copy of your original game file.
The vast majority of the information that your Undertale save file contains is stored as a series of 512 flags. These flags can contain a wide variety of information, from the pie flavor you picked to whether or not you remembered Heats Flamesman's name. The flags can be viewed using Flowey's Time Machine and can also be edited in a few different ways. For example, changing the "fun" value in your save file can trigger unique "fun" events like a phone call or a unique room change.