Substack

Substack was founded in 2017 by Chris Best, the co-founder of Kik Messenger; Jairaj Sethi, a head of platform and principal developer at Kik Messenger; and Hamish McKenzie, a former PandoDaily tech reporter. Best and McKenzie have said Ben Thompson's Stratechery, a subscription-based tech and media newsletter, was a major inspiration for their platform. Best acts as CEO of the company.

In 2019, Substack added support for podcasts and discussion threads among newsletter subscribers.

By November 2021, the platform said it had more than 500,000 paying subscribers, representing over one million subscriptions.

In January 2022, Substack announced that it would begin private beta testing of video functionality on its platform. In November, it launched Substack Chat, where content creators could create private group chats with subscribers. The same year, the company launched the Substack Reader app for iOS, followed by an Android version six months later.

In April 2023, Elon Musk spoke with Substack's leadership about purchasing the platform, but his offer was rejected. The same month, Substack implemented a Notes feature, which allows users to publish and repost short-form content. This microblogging feature has been compared to Twitter, and many outlets considered it a response to changes at Twitter under Musk's ownership. Musk criticized Substack Notes, and Twitter began censoring links to Substack.

In November 2023, Substack introduced new video creating and editing tools, and content creators started launching original shows on the platform.

In April 2024, Substack partnered with Spotify to enable podcasters to distribute episodes on both platforms and added new editing features for podcasts. In June 2024, Substack announced a year-long development initiative for TikTok creators called Creator Studio, and added five-minute video capabilities to the chat function. Video was also added to Notes.

By November 2024, Substack had four million paid subscriptions.

Criticism

Privacy and security incidents

On July 28, 2020, Substack accidentally exposed users' email addresses by putting them in the "cc" field instead of "bcc" in a privacy policy update email regarding the California Consumer Privacy Act. It acknowledged the mistake on Twitter.

In February 2026, Substack disclosed an October 2025 security breach in which a third party gained access to email addresses, phone numbers, and other internal metadata. According to The Verge, the data breach was noticed on February 3, 2026, and has been fixed. Substack announced that it would perform an investigation to prevent this from happening again.

Content moderation and extremism

In 2020, popular platforms such as Twitter, Facebook, and YouTube began restricting or deleting accounts they claimed spread COVID-19 misinformation, and some prominent authors accused of spreading misinformation moved from those platforms to Substack. The Washington Post mentioned Joseph Mercola as a conspiracy theorist who had moved his online presence to Substack.

In January 2022, the Center for Countering Digital Hate accused Substack of allowing content that could be dangerous to public health. The Center estimated that the company earned $2.5 million per year from the top five anti-vaccine authors alone. The three founders responded via blog post affirming their commitment to minimal censorship.

Substack faced further criticism in November 2023 for allowing its platform to be used by white nationalists, Nazis, and antisemites. In an open letter, more than 100 Substack creators threatened to leave the platform and implored Substack's leadership to stop giving bigotry a platform. In response, Substack co-founder Hamish McKenzie said the company would continue to allow the publication of extremist views because attempting to censor them would make the problem worse. Creators like Casey Newton, Molly White, and Ryan Broderick left the platform as a result.