Substack vs Mailchimp: Pricing, Ownership and API (2026)

The problem

"unfortunately, substack does not have an API to continually import new subscribers. MailChimp might be the best option here." (Hacker News, July 2022)

"Is there really no easy way to sync your subscribers to an external email platform like MailerLite?" (r/Substack, July 2026)

Writers weighing Substack against Mailchimp are usually choosing between two different products. Substack is a publishing platform with a reader network and paid subscriptions built in. Mailchimp is an email marketing tool with automation and an API. This comparison uses each vendor's own pages, read on 22 October 2026, and doesn't pick a winner for everyone.

Substack vs Mailchimp at a glance

Facts as of 22 October 2026, from each vendor's own pages (linked in each row).

	Substack	Mailchimp
Cost to start	Free to publish at any list size (pricing help)	Free plan: 250 contacts, 500 sends a month, 250 a day (pricing plans)
How you pay	10% of paid subscription revenue, plus Stripe fees	Monthly plan priced by contact count (pricing page)
Paid subscriptions	Built in, via Stripe	Not shown on the marketing pricing page
Reader discovery	Recommendations, Notes and the app (On Substack)	Not listed on the pricing page
Automation	Welcome emails by subscriber type (help); Boost upsell offers	Up to 200 automation flows on Standard and Premium; up to 4 flow steps on Essentials; none on Free (pricing page)
Public API for contacts	None as of October 2026 (see the Substack API guide)	Marketing API for contacts, events and webhooks (developer docs)
Sender address	@substack.com, even with a custom domain (domain help)	Not covered in the pages we read
Export	Posts, subscribers and stats zip (export help)	Audience export as CSV (Substack's Mailchimp guide)

How does pricing compare?

Substack charges nothing to publish. If you turn on paid subscriptions, Substack keeps 10% and Stripe charges its own fees: 2.9% + $0.30 per US card payment plus a 0.7% Stripe Billing fee on recurring payments, according to Substack's cost page. A custom domain is an optional one-time $50. Your costs scale with revenue, not with list size. For worked examples, see is Substack free?.

Mailchimp charges by plan and contacts. On 22 October 2026 its pricing page showed Essentials from $13 a month, Standard from $20 a month after a 14-day free trial, and Premium from $350 a month, each subject to offer terms and rising with your contact tier. It also says "overages apply if contact or email send limit is exceeded". Monthly sends are 10, 12 and 15 times your contact count on Essentials, Standard and Premium.

One detail matters for newsletters: Mailchimp says "subscribed, unsubscribed, and non-subscribed contacts are included in your contact count", while "archived, cleaned, and deleted contacts don't count" (Mailchimp pricing plans). Archive people who leave to keep costs down.

Rule of thumb: a large free newsletter costs nothing on Substack and a growing amount on Mailchimp. A small, high-priced paid newsletter may pay more in Substack's 10% than in a Mailchimp plan, but Mailchimp's marketing pricing page doesn't list paid subscriptions, so you'd need to price in a separate way to take payments.

Who owns the subscriber list?

Both let you leave with your list. Substack says "anything you publish on Substack is yours to own" and exports posts, subscribers and statistics from Settings → Exports (export help). It also says that for publishers it generally acts as a data processor and "Substack Publishers are the data controllers of that audience" (data controller help), so consent and compliance are your job on either platform.

The practical difference is sending. On Substack, emails come from an @substack.com address and readers also follow you inside the Substack app. On Mailchimp, the relationship is plain email. If portability matters most, export regularly whichever you choose; see how to back up your Substack.

API and automation depth

This is where the two differ most.

Mailchimp. The Marketing API lets you "move contacts between your application and an existing Mailchimp audience", tag them, and "sync events in your app with Mailchimp to create powerful email automations at scale". Webhooks report subscribes and unsubscribes to your systems, and OAuth 2 lets apps act on users' accounts. That's why lead forms, shops and CRMs plug into it.

Substack. As of October 2026 there's no public API or webhook for adding subscribers or getting events out; our Substack API guide covers what does exist. Substack's own MCP server gives AI assistants read-only access to dashboard metrics, traffic and settings, but only for Bestseller publications, and "cannot publish posts, send Notes, or modify your account". Built-in automation is welcome emails for free, paid, imported and founding subscribers, plus opt-in Boost offers such as upsell emails and pre-cancel offers.

If you need event-driven email (abandoned carts, multi-step drips, CRM sync), Mailchimp fits better. If you need your Substack content in other tools, newsletterapi's Posts API serves your archive as JSON, Markdown or HTML, and its embeds and content webhooks fire when you publish. See also Substack webhooks.

Which should you choose?

• Choose Substack if you're a writer building a free or paid newsletter, want payments built in, and want reach from recommendations and Notes.
• Choose Mailchimp if you're a business sending marketing email, need automation flows, segmentation and integrations, and don't need paid subscriptions.
• Running both? Substack has no subscriber sync, so you'd move people by export and import, and only with consent that covers both senders. See syncing Substack to Kit or HubSpot for the patterns.

How do I move from Mailchimp to Substack?

From Substack's Mailchimp guide:

1. In Mailchimp, go to Audience → All contacts → Export Audience and download the CSV zip.
2. Find your Campaign archive page URL under Forms, and export campaigns via Account & billing → Manage my data → Emails.
3. In Substack, open Settings → Import/Export, unzip the audience file and upload the CSV.
4. Under Import posts, enter the archive URL and upload the campaigns zip without unzipping it.
5. Remove Mailchimp's footer and banner from imported posts if they appear.

Substack warns that Mailchimp "may include only up to 20 emails in your campaign archive". Your list will be screened too: Substack requires "lists contain only those who have explicitly opted in" and may hold one for review (import rules). Only import contacts who subscribed to your newsletter, and archive the rest in Mailchimp. More on this in importing posts to Substack and adding subscribers safely.

Going the other way? Export your list and posts from Substack's Exports page, and check that your readers' consent covers being emailed from a new tool before you import them anywhere. To get access to newsletterapi, email hello@newsletterapi.io.