What is Substack?

Substack is a platform for subscription-based newsletters and podcasts. The material tracks concerns about AI’s use of its content and the quality of writing it hosts.

• Apr 2026 - Steve Newman described a tool that takes the full text of each Substack post or podcast transcript and feeds it into a language model for summarization, with a static prompt.
• May 2026 - Matthew Prince said that OpenAI can buy a single Substack subscription, slurp all the information, and publish it to everyone, calling this ‘exactly what’s happening right now.’
• Jun 2026 - Grant Sanderson argued that AI systems may not be good at discriminating between an A essay and something truly insightful and followable on Substack, instead preferring uninsightful content.