Best Newsletter Platform With an API (2026): What Each API Can Do

What the API covers. Kit’s current API is V4 (V3 still works but is deprecated). The docs say that on an eligible plan you can “create and send broadcasts to your subscribers, manage your email list through tags and custom fields, import purchase data” and more. The create-broadcast endpoint saves a draft when send_at is null and schedules the send when you pass a timestamp. Pagination is cursor-based.

Webhooks are the best of the five. The newer /v4/webhook_endpoints system lets one endpoint subscribe to many events. It batches 1 to 100 events per delivery, signs each delivery with an X-Kit-Signature HMAC-SHA256 header, gives every event a UUID for dedupe, and retries failures “8 attempts over ~41 hours”. Available events include subscriber.created, subscriber.unsubscribed, subscriber.bounced, subscriber.tag_added, subscriber.sequence_completed, broadcast.sent and post.published. Click, open and purchase events are listed as “Planned”, not live.

Limits. 120 requests per rolling 60 seconds per API key, or 600 with OAuth. Some endpoints, including bulk and purchase creation, require OAuth.

The gotcha. Kit’s response-codes page lists a 401 when “an account no longer has access to apps (due to their trial lapsing, being on a free account…)”, and the webhook docs say the same for “a free plan or a lapsed trial”. So the Free plan that covers 10,000 subscribers doesn’t include the API. Creator is $39/mo on monthly billing at up to 1,000 subscribers and $139/mo at up to 10,000, per the price table behind the slider on Kit’s pricing page.

Pick it if your app needs to schedule sends and react to subscriber events, and you’ll pay for Creator anyway.

What the API covers. REST at https://connect.mailerlite.com/api with Bearer-token auth. The resources are subscribers, groups, segments, fields, automations, campaigns, forms, webhooks, batching and an e-commerce API. You can pin an API version with an X-Version header, which is a nice touch if you’ve ever been broken by an unannounced change. Official SDKs exist for PHP, Go, Node.js, Python, Ruby and Rust.

Sending. POST /api/campaigns creates a campaign, POST /api/campaigns/{id}/schedule sends it instantly, schedules it, or uses timezone-based or smart sending, and /cancel pulls it back. Two plan gates matter. Custom HTML content via the API requires “the Advanced plan” (Power on the pricing page, $39/mo at 1,000 subscribers), and the pricing page says “On Free, API and MCP access is limited and doesn’t include sending.”

Webhooks. There are 14 events, including subscriber.created, subscriber.unsubscribed, subscriber.bounced, subscriber.spam_reported, subscriber.automation_completed, campaign.sent, campaign.open and campaign.click. Payloads carry an HMAC-SHA256 Signature header. Your endpoint has 3 seconds to answer, and failures retry three more times after 10, 100 and 1,000 seconds. Open and click events must be batched.

Limits. 120 requests per minute globally. Imports are limited to 5 per minute, so use the batch endpoint for bulk work.

Pick it if you want full send-from-code for the least money. Comfort is $19/mo at 1,000 subscribers. Budget for Power if you render your own HTML.

What the API covers. beehiiv’s API is on every plan, Free included. It covers subscriptions (single and bulk create), automation journeys, newsletter lists, exports, ad network reports and posts, and it supports OAuth scopes per resource.

Sending is gated hard. The create-post endpoint “is available to publications on the Pro and Enterprise plans.” It accepts structured blocks or raw HTML in body_content, but <style> tags are stripped during sanitization, so inline your CSS. Creation is asynchronous. You get a 201 with an id, and fetching the post too early returns 202 until it’s ready. Pro is $109/mo at 1,000 subscribers and $239/mo at 10,000 on monthly billing.

Webhooks. The docs say webhooks are “only available for paid users on the Lite plan and above”. The pricing page puts Lite at 3 webhooks and Pro at unlimited. Deliveries go through Svix, so you verify svix-signature headers. The events cover subscriptions (created, confirmed, deleted, upgraded, downgraded, paused), posts (sent, scheduled, updated), surveys and podcasts.

Limits. The rate limit scales with plan: 30 requests/min on Free, 180 on Lite, 500 on Pro and 800 on Enterprise. Each key and each OAuth token gets its own allowance.

Pick it if your newsletter is already on beehiiv and you mainly need to sync subscribers. If you need to publish from code, only Pro will do.

What the API covers. v3 REST at https://api.getresponse.com/v3 with an X-Auth-Token header. The surface is wide: contacts, campaigns (lists), tags, custom fields, autoresponders, newsletters, RSS newsletters, imports, shops, webinars, workflows, statistics and transactional emails. Note that GetResponse says unused API keys expire after 90 days.

Sending. POST /newsletters “creates a new newsletter and puts it in a queue to send”, and the method is capped at 256 calls per day. That’s plenty for a newsletter, but too few if you planned to fire one-off sends per user. The pricing page lists the transactional-email API on Enterprise only.

Webhooks. There are 13 events, including message opened, link clicked, contact subscribed, contact unsubscribed and custom field changed. Optional batching groups up to 100 events. Your endpoint must reply within 5 seconds with {"status": "OK"} in the body, or GetResponse retries, even on a 2xx. There is no payload signature. The docs suggest putting a secret in the URL’s query string instead.

Limits. These are the most generous here: 80 requests per second, 30,000 per 10-minute window and 10 concurrent requests.

Pick it if you’re doing heavy contact syncing and want headroom. Starter is EUR 16/mo at 1,000 contacts.

What the API covers. v3 REST at a per-account base URL (https://<your-account>.api-us1.com/api/3/). Third-party apps should always read that URL from the user’s Developer settings, not build it. Auth is an Api-Token header. It’s the deepest API here: contacts with bulk import of up to 250 per request, custom fields, segments, deals, e-commerce and campaigns. The campaign endpoints let you create, schedule, pause, resume, stop and send a test.

Webhooks. There are many events: subscribes, unsubscribes, campaign sends, opens, clicks, replies and bounces, plus deal and SMS events. You can filter by who caused the event (contact, user, API or system). The docs say delivery is “at least once” and that “Webhooks are never retried”, so a missed delivery is gone. Plan to reconcile with periodic API pulls.

Limits. 5 requests per second per account, shared across every integration on that account. Collections return 20 records by default and 100 at most.

Why it’s last for this use case. The API is excellent if you’re building marketing automation or CRM. For a newsletter, the account-wide 5 req/s, the lack of webhook retries and a pricing page that shows no prices (as of 2026-10-12) make it hard to recommend to an indie maker.