Migrate from Kit to Unitpost

Before you start

• A Kit V4 API key: Settings → Developer → Add a new key, under V4 API Keys. V3 keys (api_key and api_secret) don't work.
• Kit's docs describe no read-only API key. The importer only reads; delete the key in Kit when the move is done.
• If Kit refuses a key you just made, check Billing in Kit: Kit answers the same way for a bad key and for an account whose plan or trial doesn't include API access right now.
• A Unitpost API key for your app with emails:send, plus contacts:write and segments:write if your signup form adds contacts, created in API keys.
• A second Unitpost key for the migration steps, with templates:write and webhooks:manage, saved as UNITPOST_MIGRATION_KEY. Keep it out of your app and revoke it once the move is done.
• Access to your DNS host.

The cut-over plan

Kit keeps sending until the last step, so there is no gap in delivery.

1. 1

   Run the Migration Assistant

   Paste the V4 key in Settings → Migration. The preview lists the unconfirmed subscribers it leaves out, your Kit segments and sequences, and the templates whose Liquid needs review. Suppressions are written before contacts, so bounced and complained addresses land unsubscribed.

2. 2

   Verify your domain

   Kit's API shares sending addresses, not DNS records. Open Domains and publish the records shown: MX and SPF on unitpost.<your domain> and a DKIM TXT under _domainkey. They don't replace Kit's records, so both stay authenticated. Keep your single _dmarc record.

3. 3

   Review Liquid and publish

   {{ subscriber.first_name }} is now {{first_name}} and {{ unsubscribe_url }} is {{unsubscribe_url}}; custom fields map by key, and filters such as | default: are dropped. Unitpost fills flat {{name}} placeholders only, so {% if %} blocks and Kit-only tags such as {{ address }} stay as written for you to rewrite. Publish with PATCH /api/v1/email/templates/{id}.

4. 4

   Rebuild segments as filters

   Recreate each Kit segment in Segments as a dynamic segment on contact fields. Your tags already came over as static segments with their members.

5. 5

   Rebuild sequences

   Each sequence email is a template named after its sequence and position. Rebuild the order and delays in Automations if your workspace has early access; until then, send them from your code on the same schedule.

6. 6

   Point signups at Unitpost

   Kit forms and landing pages keep adding subscribers to Kit. Send signups from your own form with POST /api/v1/contacts and add the contact to a segment where you used a tag. Kit's create call updates an existing subscriber; here an existing contact answers 409, and PATCH /api/v1/contacts/{id or email} updates it.

   signup.ts

   // Before: Kit
   const kit = { "X-Kit-Api-Key": process.env.KIT_API_KEY, "content-type": "application/json" };
   await fetch("https://api.kit.com/v4/subscribers", {
     method: "POST",
     headers: kit,
     body: JSON.stringify({ email_address: "user@example.com", first_name: "Ada" }),
   });
   await fetch("https://api.kit.com/v4/tags/" + TAG_ID + "/subscribers", {
     method: "POST",
     headers: kit,
     body: JSON.stringify({ email_address: "user@example.com" }),
   });
   
   // After: Unitpost
   import { Unitpost } from "unitpost";
   const unitpost = new Unitpost(process.env.UNITPOST_API_KEY);
   const { error } = await unitpost.contacts.create({ email: "user@example.com", first_name: "Ada" });
   // 409 conflict: the contact already exists. Kit's call upserts; update with contacts.update.
   if (error && error.code !== "conflict") throw new Error(error.message);
   await unitpost.segments.addMember("seg_123", { contact: "user@example.com" });

7. 7

   Re-key and enable webhooks

   Kit signs deliveries with X-Kit-Signature. Unitpost signs each body with a whsec_ secret in svix-id, svix-timestamp and svix-signature. Rotate the secret in Webhooks to see it, update your handler, then set status to enabled. Unitpost also sends per-message events Kit doesn't, such as email.delivered and email.opened.

8. 8

   Test, move traffic, then delete the key

   Send each template with POST /api/v1/email/templates/{id}/test-send and fire POST /api/v1/webhooks/{id}/test at each endpoint. Send your next broadcast from Unitpost as a campaign to a small segment first, then to everyone, and delete the Kit key.

Before you cancel Kit

• Export subscribers as CSV, including unconfirmed ones, which the importer leaves out.
• Note who is in each Kit segment if you'll rebuild it; Kit's API can't list segment members.
• Write down each visual automation and rule, with its trigger and timing.
• Move or close your products and paid newsletters; Unitpost doesn't bill readers.
• Delete Kit's DNS records once no mail goes through Kit. Keep _dmarc and Unitpost's records.
• Delete the Kit API key you used for the import.

Facts about Kit checked 2026-11-05. Providers change their APIs and plans; check their docs before you rely on a detail.