Board Thread:General Discussion/@comment-28683979-20161118172904/@comment-27701762-20161118202158

Debug mode is a mode of gameplay put in by developers to help them search for bugs in the game. The mode is then removed or hidden in the final product. It can only be accessed by manipulating game files. If you want to learn how to access debug mode, you can Google "Undertale debug mode" and you'll get some hits.

There's not really any warrant for a page on this Wiki, since debug mode itself mostly just shows information that would normally be hidden from the player. Those pieces of information, when they are relevant, are put onto the individual pages.

If you want a full list of what can be done with debug mode, you can check out this page.