Undum (undum.com) is an authoring system for CYOA-style stories playable on web browsers. Undum describes itself as "a client side framework for hypertext interactive fiction games". Undum was created by I.D. Millington in 2010. It was nominated for Best Technological Development at the XYZZY Awards 2010.
- Undum.com (old link). Old homepage. An English tutorial (old link) and a Russian tutorial (old link) were both available.
- Markers and highlighters: a gamedev metaphor (old link) - article comparing Undum, Ramus, and Squiffy.