How to Sync Substack Subscribers to Kit or HubSpot

The problem

"Is there really no easy way to sync your subscribers to an external email platform like MailerLite? How do the big accounts do it, are they literally just exporting and re-importing all the time?" (r/Substack, July 2026)

"Substack is where people subscribe to my newsletter. Kit is where my actual marketing lives." (Prisca Onyebuchi, LinkedIn, June 2026)

In our review of public Reddit, X and forum posts (October 2026), getting subscribers out of Substack and into another tool was one of the pains most often tied to money already being spent: 19 coded forum sources and 20 distinct social sources, and many of those people already pay for Kit, ActiveCampaign, HubSpot or Zapier. The requests go back years: "Any ideas on how to sync Unsubscribes between Substack and the crm?" (r/Substack), and an agency asked Make for a scenario that would "unsubscribe people inside GHL once they unsubscribe from Substack" (Make community).

The answer as of October 2026 is unglamorous: export, import, repeat. This guide makes that repeatable and safe.

Is there a native Substack integration for Kit or HubSpot?

No. Substack has no public write API, no webhooks and no Zapier app (see Substack integrations). In the Make community, a reply to "Any chance an integration with Substack is coming?" was "Don’t keep your hopes up, sorry" (Make, 2024). The Gmail-notification trick many people used broke when Substack removed addresses from new-subscriber emails in March 2026 (what changed).

Option	Works in October 2026?	Notes
Native Kit or HubSpot connector	No	None exists
Zapier, Make or n8n trigger	No official trigger	Community workarounds depend on email parsing or browser sessions
Weekly export → import	Yes	Manual, about 10 minutes, reliable
Publisher API lookup	Partly	Confirms one known email where enabled; can't list subscribers (see API overview)
Your own signup form → both tools	Yes, for new readers	Collect consent for both on one form, then hand off to Substack's /subscribe

How do I set up a weekly export-and-import sync?

1. Export from Substack. Subscribers → All subscribers → the three dots → Export. "All columns" adds activity such as last open and post views; "visible columns" includes "the date someone subscribed and their type of plan" (export help). To export only new people, filter or segment by start date first (dashboard help).
2. Diff against last week. Keep each export with its date. New emails go to step 3; missing emails go to the unsubscribe pass below.
3. Map the fields (table below) and add a tag such as substack-2026-10-21.
4. Import into Kit or HubSpot into a list or tag that only receives what those people agreed to.
5. Run the unsubscribe pass in both directions.
6. Log the run: date, rows added, rows removed. Missing a week is how people slip through.

How do Substack's export fields map to Kit and HubSpot?

Substack export column	Kit	HubSpot	Notes
Email	Email address (required: "There must be a column for your subscribers' email addresses at the very least")	Email	The only safe key; Substack exports no names (export help)
Subscription date	Custom field, e.g. substack_joined	Custom date property	Useful for welcome timing
Subscription type (free, paid, founding, gift, comp)	Tag, e.g. substack-paid	Custom property or list membership	Values per the dashboard help
Activity / opens	Custom field (optional)	Custom property (optional)	Snapshot only; it goes stale
Revenue	Usually skip	Custom property if finance needs it	Personal data; keep access tight
Your tags	Comma-separated tags column	Static list	Kit: "with each Tag separated by a comma"

Two import behaviours to know before your first run:

• Kit overwrites. Kit says "we will replace any existing data we have on your subscribers with the data you provide in your import file", including blanks, though existing tags are kept (Kit import help). Leave out columns you don't want to replace.
• HubSpot's quick import skips advanced settings. Its import page says the quick tool skips "advanced settings (e.g., marketing contacts, overwriting property values)", so use the advanced import when you need to set marketing-contact status. Files must be .csv, .xlsx or .xls with a header row (HubSpot import help).

The one-off version of this move, including a full Kit walkthrough, is in exporting Substack subscribers.

How do I sync unsubscribes?

Unsubscribes are where most syncs fail, and where the legal risk sits.

1. Substack → Kit/HubSpot. Anyone in last week's export but not this week's has left (or bounced). In Kit, tag them and use the Unsubscribe bulk action (Kit bulk actions). In HubSpot, import them as "List of contacts to opt out of emails"; HubSpot then sets "Unsubscribed from all email" to true (HubSpot opt-out import).
2. Kit/HubSpot → Substack. If someone unsubscribes in your marketing tool, decide whether that also means your newsletter. If it does, remove them from your Substack Subscribers page.
3. Optional early signal. Substack's "Canceled free subscription" notification sends "an email confirmation that their email has been disabled and removed from your list" (help). We haven't confirmed it still includes the address after the March 2026 change, so treat the export diff as the source of truth.
4. Never re-add. Someone who unsubscribed from Substack can't be re-added there anyway; they have to subscribe again themselves (import help).

What are the consent and deliverability risks?

• Consent doesn't travel automatically. A commenter warned: "You may want to consider certain anti-spam laws because those people didn't opt in to your site. They opted in to Substack." (r/Substack). Kit requires that "Each person on your list is required to have provided their permission to receive your marketing emails" (Kit FAQ). HubSpot's Acceptable Use Policy prohibits collecting email addresses "without their consent". In a popular sync tutorial's comments, one reader cautioned: "Unless you have their express permission, it is illegal to begin selling them other stuff outside of that Substack agreement." (Me & Orla).
• You're the controller. Substack's Publisher Agreement says you are "the controller of your List" and must comply with data-protection law "including in your off-platform use".
• Don't double-send. If the same person gets your newsletter from Substack and a marketing email from Kit on the same day, complaints rise for both senders. Split by purpose: Substack for the newsletter, Kit or HubSpot for sequences people opted in to.
• Expect tag loss going the other way. Moving people from Kit into Substack drops metadata; one writer worried about "losing all my metadata like tags, when moving someone from Kit to Substack" (r/Substack).

The cleanest fix for new readers: one signup form that asks for consent to both, records it, then hands the reader to Substack's /subscribe page.

What not to do

• Don't scrape your dashboard or run a hosted browser with your Substack cookies to "sync" in real time. It conflicts with Substack's terms and puts the account at risk.
• Don't import Substack subscribers into marketing automations they never agreed to.
• Don't push CRM contacts into Substack to "complete" the sync. Substack's guidelines prohibit importing contacts without consent.
• Don't skip the unsubscribe pass. Emailing people who left is the fastest way to complaints.

Is there a tool for this?

newsletterapi offers analytics and sync from your own exports: drop in a weekly Substack export and get a clean diff of new, changed and unsubscribed people, mapped for Kit or HubSpot, with consent flags kept. It never logs in to Substack for you.