By 
Toby Fox announced a two-day celebration for the 10th anniversary of Undertale, and noted this will involve a two-day live stream event showing a run of the game. That will appear September 20-21, 2025. The creator of the series also used a Fall 2025 newsletter to share an update on Deltarune Chapter 5 that included a new release window. It could launch in the second half of 2026, following the 2025 launch of 3 and 4.
In the case of Undertale, we’ll get to watch Toby Fox play the game for its 10th anniversary on Fangamer’s Twitch channel. That will be the only source. It’s unknown if they’ll be only archived on Twitch or also available elsewhere. Each day, it will start at 4pm PT/7pm ET. The creator did note in the Fall 2025 newsletter that the last time this type of stream happened, “it took over 8 hours…”
As for the Deltarune Chapter 5 update, Toby Fox noted the team is currently at the “making the game” phase of development. The developers still need to work on localizations and the porting process. That will be followed by finishing it up and Q&A testing before the release. Fox noted, “Factoring the localization and testing… I don’t think that the game will be released in the first half of 2026.” The more detailed assessments said early areas and regular enemies are mostly done. As for the story, Fox also said, “Probably around 85% of cutscenes have been created up to a first draft state, however, of those at least 20% or so will require more polish.”
Undertale is available on the Switch, PS4, Vita, Xbox One, and PC, and the 10th anniversary live streams will be at 4pm PT/7pm ET on September 20-21, 2025. Deltarune Chapters 1-4 are available on the Switch, Switch 2, PS4, PS5, and PC, with Chapter 5 due in the second half of 2026.
