CoStack automatically matches you with complementary newsletters in the productivity & self-help space — and swaps recommendations so you both grow. No cold DMs, no guesswork.
Three simple steps to start growing your newsletter with trust-based, automated recommendations.
Tell us about your newsletter — your niche, your audience, and the kind of writers you admire.
Our algorithm finds complementary writers whose readers will genuinely love your work.
Auto-swap recommendations and watch your subscriber count climb — no cold DMs required.
CoStack is designed specifically for indie Substack writers in the productivity and self-help space. If you write about how people think, work, and live better — you belong here.
We match you with newsletters that complement — not compete with — your work. A deep work writer gets paired with a note-taking writer. A habits newsletter swaps with a mindfulness one. Your readers discover writers they'll love, and theirs discover you.
The data is clear — mutual recommendations are the fastest way to grow a newsletter audience.
Newsletter cross-promotion consistently outperforms social media for growing engaged readership.
Writers who cross-promote with complementary newsletters grow their audience significantly faster.
Join now as a founding member and lock in free access while we build the community.
Start free. Upgrade when you're ready to go further.
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Everything you need to know before joining.
We look at your niche, audience size, and writing style to find newsletters that complement — not compete with — yours. A deep work writer might get matched with a note-taking newsletter, so both audiences discover relevant new content.
Never. CoStack never accesses or shares your subscriber list. We only facilitate recommendation swaps — your readers choose whether to subscribe to recommended newsletters on their own.
You're always in control. You can review every match before it goes live and decline any recommendation swap that doesn't feel right. No obligation, no awkwardness.
Substack's recommendations are one-way — you recommend someone and hope they notice. CoStack guarantees a mutual swap with a vetted, complementary writer, so both of you benefit equally.
The free plan gives you 1 active recommendation swap, access to our basic matching algorithm, and community access. It's enough to get started and see results before upgrading.
Be among the first writers to access CoStack. We'll notify you as soon as we launch.