There are two *online, evolving, collaborative "foundational text" projects for research mathematicians* that I am aware of: (1) [The Stacks Project][1] for algebraic geometry (2) [Kerodon][2] for categorical homotopy theory I find them admirable, valuable and suited to our times - sort of Bourbaki for the internet age. I'd like to know if there are others of the *same nature* that are ongoing or in the offing. Please note that I am not looking for texts or monographs available online which is why I have highlighted the adjectives in the first line. [1]: https://stacks.math.columbia.edu [2]: https://kerodon.net/about