Paid subscriptions to its hundreds of thousands of newsletters exploded to more than one million late last year from 50,000 in mid-2019. (The company won’t disclose the number of free subscribers.)

Executives hope to eventually take the company — which has raised more than $82 million and is said to be valued at $650 million — public.

Executives want users to create “personal media empires” using text, video and audio, and communicate with subscribers through expanded comments that could feature GIF images and profiles for readers.

[...] trying to put “the Substack brand front-and-center,” building up its app as a destination on the backs of writers.

This month, the company announced a podcasting expansion.

[...] build an alternative revenue model that entails readers paying for Substack first, and publishers second, instead of the other way around,”

Publishing on Substack is free, but writers who charge for subscriptions pay 10 percent of their revenue to Substack and 3 percent to its payment processor, Stripe. The company also offers hefty advances to a small group of writers, whose identities it refuses to divulge.

It refuses to chase advertising dollars. “Over my dead body,” Mr. McKenzie once wrote. “The antithesis of what Substack wants to be,” Mr. Best said.

Substack has resisted pressure to be more selective about what it allows on its platform. Employees of Twitter who worried that its content moderation policies would be relaxed [...], were told to not bother applying for jobs at Substack.

Medium pared back its editorial publications to pursue a more Substackian model of “supporting independent voices.”