Everything online eventually turns into social media. Substack began as one of many newsletter sites that made it easy for writers and readers to use mailing lists to send and receive texts in longer forms than those provided by Twitter (the irony being that microblogging à la Twitter had undermined the world of long-form blogging that preceded it). But then Substack added its Notes section, which behaves a lot like Twitter: writers of newsletters, as well as their readers, can post short notes and share quotations from and links to Substack and other sites. As with other social-media sites, the goal is to keep people on Substack as much as possible. (Andrew Shields, #111Words, 31 December 2025)