I asked ChatGPT what it knows about Twtxt 😂 And surprisingly it’s rather accurate:

Twtxt is a minimalist, decentralized microblogging format introduced by John Downey in 2016. It uses plain text files served over HTTP—no accounts, databases, or APIs.
In 2020, James Mills (@prologic@twtxt.net) launched Yarn.social, an extended, federated implementation with user discovery, threads, mentions, and a full web UI.
Both share the same .twtxt.txt format but differ in complexity and social features.